Getty Images

At a Mobile World Congress keynote panel in late February on the timing of 5G devices, Qualcomm President Cristiano Amon declared with confidence, "The phones are ready; we're just waiting for the networks." About an hour later, in a briefing room a mere 10 feet below that keynote hall, AT&T Chief Technology Officer Andre Fuetsch told CNET, "The issue is devices. Frankly, we're waiting on the devices."

After years of work on 5G networks, hyped as the life-changing foundation for tech trends like augmented reality and telemedicine, the super-fast wireless technology has finally gone live. Carriers are turning on their networks, and virtually every major Android handset maker has talked up plans to launch a 5G device this year.

Now playing: Watch this: Galaxy S10 5G camera, 5G demo at MWC 2019

There's been a whirlwind of 5G news. This spring, 5G networks went live in the US and South Korea. In the US, Verizon turned on its 5G service in early April in Chicago and Minneapolis. Sprint followed in June, with 5G service in Atlanta, Dallas-Fort Worth, Houston and Kansas City. And various handset makers, including Samsung and LG, have started selling their first 5G devices. T-Mobile's turned on its network in six cities, including a test we conducted in New York, but the coverage is still minimal.

Samsung, the world's biggest smartphone vendor, has launched the Galaxy S10 5G across all four nationwide networks in the US, including on T-Mobile on Friday. LG'S V50 ThinQ is also live on networks such as Sprint and Australia's Telstra. The OnePlus 7 Pro launched on EE's fresh 5G network in the UK.

At MWC in February, Oppo talked up its first, not-yet-named 5G phone. Also at MWC, Huawei showed off its 5G-powered Mate X foldable and Xiaomi detailed its Mi Mix 3 5G. The show also marked the debut of ZTE's Axon 10 Pro, while Sony and showed off prototypes for devices they'll launch this year.

That doesn't mean you should jump on the 5G bandwagon just yet. Here are a few reasons to wait a bit.

Sparse coverage

AT&T says it had the first mobile 5G network in the US, but when it comes to where you can actually tap into the next-generation service, things get a little mysterious.

"They're small pockets in the cities," Fuetsch said earlier this year, noting that all of the customers using the Netgear Nighthawk 5G Mobile Hotspot are small businesses. "We haven't disclosed them publicly."

Juan Garzon/CNET

AT&T and Verizon have invested in superhigh frequency radio airwaves known as millimeter wave spectrum, which brings tremendous speed and capacity. The downside of that high capacity is limited range.

How limited? Think a block or two. So even if AT&T and Verizon say they have 5G coverage in a city, you may struggle to actually get on the network, even with a compatible device.

A Verizon spokesman admitted earlier this year that the initial deployment would be small. That's exactly what CNET's Jessica Dolcourt found in April when she traveled to Chicago to test the Motorola Moto Z3 phone with a 5G Moto Mod. Dolcourt at times detected the high download speeds promised by Verizon -- between 450 Mbps to 1Gbps in less than 30 milliseconds -- but those speeds were few and far between.

"I'd like to be able to say that using Verizon's 5G was a mind-blowing experience, with download speeds beyond my wildest imagination," she wrote. "I wish I could tell you that I downloaded entire albums of music and streamed video instantly. Unfortunately, all I can say after a long day is that I found it confusing. Frustrating. Absolutely insane."

A second test of the Verizon network was more impressive than the first attempt, with data speeds a month later blowing past 1Gbps. And Verizon at least has launched its service for mobile use. AT&T turned its network on in December but still hasn't made access available for consumers. A CNET speed test of its 5G network in the closed off Warner Bros. studio in Los Angeles, however, nabbed our highest peak speeds.

At MWC in February, T-Mobile Chief Technology Officer Neville Ray told CNET that his company has fired up millimeter wave spectrum that supports the upcoming Galaxy S10 5G, but that it likely won't market the network since the coverage area is so small.

Ray said T-Mobile's full 5G launch will happen in the second half of the year. He didn't specify when, but there may not be phones that run on the company's broader 5G network until the fourth quarter, or even early 2020. That's because devices for T-Mobile's network will require Qualcomm's upcoming second-generation modem, the X55, and that isn't yet available for devices.

Smartphones coming in time for the holidays later this year will still use the first-generation modem, the X50, Qualcomm's Amon said in an interview at MWC.

"There are some [handset makers] who are aggressive with their launch dates," he said. "We could see some X55s, but most of the smartphones coming from Q2 2019 all the way to the holiday season will be ... X50."

A T-Mobile spokeswoman would say only that the broader network launch would happen in the second half.

Both Ray and Fuetsch are shooting for nationwide coverage using lower frequency (and longer range) spectrum by 2020.

The carrier with the biggest early 5G coverage could actually be Sprint. Yes, that Sprint. The company claim roughly 2,180 square miles of coverage, which covers 11.5 million people, makes it the largest 5G network in the country.

CNET's Lynn La traveled to Dallas to try out the LG V50, a $1,152 5G phone distinguished by its second-screen attachment (the attachment won't be made available in the US). She found speeds weren't as fast as on Verizon's network, but Sprint's "coverage was impressively consistent."

"Unlike Verizon's 5G network, you don't have to be near or within eyesight of a node to get high-speed data from Sprint," La wrote.

Expensive phones

5G phones don't come cheap, with most of them breaking the $1,000 mark.

At the high end of the spectrum is Huawei's Mate X. The foldable phone will cost a jaw-dropping 2,300 euros ($2,600) when it eventually goes on sale (Huawei planned to launch it midyear, but it has delayed its release). That's pricier than feared, even though it's one of the world's first foldable phones.

Huawei's second 5G phone is the Mate 20 X 5G. It's been pulled by EE in the UK, but should retail for £999 (or about $1,279 in the US and AU$1,856 in Australia), the device has a huge 7.2-inch display, a 4,200mAh battery and a triple rear-camera setup. EE, Vodafone, Three and O2 were supposed to carry the Mate 20 X 5G, but it's clear if it'll actually show up. It won't be coming to the US.

EE's network, by the way, is up in five cities. And despite some strong speeds, coverage remains inconsistent, according to our early speed test. (Sense a theme here?)

Verizon began selling the Galaxy S10 5G in May. Priced at $1,300 -- $300 more than the Galaxy S10 Plus -- and originally unveiled during Unpacked, it has a 6.7-inch display, four rear cameras and the ability to wirelessly charge other devices. The device also became available on Sprint on June 21, followed by AT&T and T-Mobile.

Samsung also will launch a 5G variant of its foldable Galaxy Fold, but that phone's launch has been delayed due to screen issues. It hasn't yet detailed how much the 5G model will cost, but the 4G variant is $1,980.

The LG V50 ThinQ is available for Sprint users for $1,152, and Verizon is selling the phone for $999. It will come to T-Mobile and AT&T later in the year.

On the other end of the pricing spectrum are phones from Motorola/Lenovo and Xiaomi. Xiaomi's Mi Mix 3 5G retailed for 599 euros ($679) when it hit the market in May, an amount that's less than many 4G phones today.

Lenovo's first 5G device was 2018's Motorola Moto Z3. Its successor, the Moto Z4, launched in May without much fanfare. Like the Z3, the Z4 connects to 5G with a Moto Mod modular accessory, which attaches to the back of the phone using magnetic pins. The phone is $499 and the Mod costs extra, but for a limited time you can get both for $440, making the Z4 the cheapest 5G phone yet.

As for a Motorola phone that wouldn't need an accessory to connect to 5G, the company is working on making such a device, but you'll have to wait much longer. Doug Michau, Motorola Mobility's director of technical sales and operations, said that phone would come much later than early 2019. More specifically, Michau said it would launch in "definitely less than three years, but no time frame yet."

Ultimately, the additional features added to 5G phones "will determine the premium," Creative Strategies analyst Carolina Milanesi said. "Rest assured, there will be one."

Wireless plans also cost more. Verizon 5G service is a $10 premium over the regular plan, but your first three months are free. Sprint's Premium Unlimited plan to access 5G costs $80 to $90 a month.

Carriers are spending billions of dollars to build out 5G networks. Device makers need to use pricier components like 5G radios and bigger batteries. Those higher costs will likely flow down to you through more expensive service and phones. And the shift to 5G gives carriers and phone makers the chance to charge more for those top speeds at a time when they're not selling as many devices.

"Initially, the price of 5G phones will be higher than 4G phones, that's for sure," Yenchi Lee, senior director of product marketing for MediaTek's wireless communications business, said in an interview at MWC. The company at the trade show unveiled its first 5G modem, which'll be in smartphones in early 2020.

Once chips like Qualcomm's new integrated Snapdragon 5G processor hit the market next year, companies making less expensive phones will also be able to include 5G in their devices.

"We're trying to get to 5G not just to that flagship tier but to other tiers as fast as we can," Qualcomm's Amon said. The integrated chip will be in phones in the first half of 2020.

Compatibility issues

Thanks to everyone embracing 4G LTE, we'd finally gotten to the point where phones could be taken to almost any carrier and still work. Then 5G came along.

Though everyone is using the same wireless technology, the carriers are employing different bands of spectrum. And the first-generation chip and antennas can't tap into all those frequencies at the same time.

Instead, whatever 5G phone you buy that has Qualcomm's X50 modem (which is basically any 5G phone except those from Huawei) will be tied to a specific carrier. The 5G phone you buy for Verizon will work only on Verizon's 5G network.

Once the X55 chip and new Qualcomm radios are out, a phone will be able to run on all major spectrum bands, all over the world. That means we can finally get unlocked 5G phones -- if that's what the handset makers choose.

No killer apps yet

Throughout MWC, countless booths showed off how 5G can change the experience on your phone, with, for instance, video calls and polished console-level games running smoothly, thanks to much of the processing power being handled remotely.

But consumers aren't going to pay a premium just to eliminate a little buffering.

Andrew Hoyle/CNET

"The industry's challenge is finding what's the killer app for 5G," said Dan Hays, a consultant for PWC.

Those apps will come, even if it takes time. Remember, until 4G improved the quality of the services, things like Uber or livestreaming through Facebook didn't exist, and watching streaming video from the likes of Netflix and YouTube didn't take off.

But in the early days, there may not be a lot of ways to take advantage of all that bandwidth.

Mobile 5G beyond phones

Though the world's biggest handset makers plan to release 5G phones as soon as possible, other, smaller players are being more cautious. HTC for one "questioned whether it was right to do [5G] on a phone." For now, at least, HTC doesn't think phones are the way to go. Instead, it's focusing on delivering 5G to customers through its 5G Hub, which'll be available in the US on Sprint's network.

"The beauty of the hub concept is it doesn't matter what device you've got," Nigel Newby-House, HTC associate vice president of product planning and go-to-market, said in an interview ahead of MWC. "Whether it's VR, notebook, tablet, this is your gateway that could be shared across devices. We're trying to spare you the cost of having 5G in your phone, tablet, etcetera."

But buying the hub doesn't automatically mean you'll have 5G speeds on a 4G phone. You'll get faster speeds only if your phone has 802.11ad, which enables WiGig Wi-Fi speeds. If your phone is older and runs only 802.11ac Wi-Fi, you'll end up with a bottleneck where the hub is trying to deliver data faster than your phone can handle.

MWC wasn't the last time we'll hear about 5G phones. But you might want to wait until next year before you rush to buy one.

Originally published on March 2 at 5 a.m. PT.

Update March 3 at 6 a.m. PT: To include background.

Update April 4 at 4:36 p.m. PT: Adds Verizon 5G network launch info.

Update June 29 at 5 a.m. PT: Adds additional background about AT&T and T-Mobile 5G tests.