"The tablet that can replace your laptop." That's what they say in those Microsoft Surface ads. But the Microsoft Surface Pro doesn't come with a keyboard -- if you want to replace your laptop, you'll need to pay $130 extra for that in the US.

The HP Elite x2 is different. Starting at the same $899 as a Surface Pro 4 (£708 in the UK or AU$1661 in Australia), HP's 12-inch tablet includes the keyboard cover that Microsoft's slate lacks. And a fingerprint sensor. And a non-proprietary USB-C charger that can power other devices as well.

And -- get this -- a design where users can actually open up the case and replace the components, including the battery, storage module, Wi-Fi chip and the colorful display. As far as we're aware, it's the first ultrathin, fanless tablet to offer such easy access.

So last month, I tried to replace my laptop with an Elite x2. Here's what happened next.

James Martin/CNET

The commute

At just under two pounds and 13.45mm thick -- with the keyboard attached -- the Elite x2 is among the most portable computers I've ever carried. I love how the fabric-covered keyboard and shiny silver kickstand snap into place, how easily it slips into my messenger bag and that it barely seems to add any weight. Sometimes I walk out the door and wonder if I forgot to pack it.

On the train, things aren't quite as easy. I use the Elite x2 on my lap, adjusting that shiny silver kickstand again and again to find the best angle, its corners digging into my thighs. The Elite can't quite lean back far enough to align with my face unless I risk it tumbling backwards. A jolt as the train comes to a stop -- the tablet pops right off its magnetic hinges. Both pieces clatter to the floor.

Enlarge Image GIF by Sean Hollister/CNET

After the spill, the Elite x2 is perfectly fine -- no damage to the strong aluminum rim or shock-resistant Gorilla Glass 4-covered screen, which HP claims it tests to military durability standards. But every time it happens over the next few weeks, I can't help but think I'd be better off with a traditional clamshell PC.

The so-called "lapabilty" problem isn't unique to the Elite x2, by the way. It's simple geometry: a kickstand and detachable keyboard take up way more room than a standard laptop bottom.

Depending on your commute and the shape of your lap, it might not be an issue at all.

The desktop

While the Elite x2 only has three visible ports -- a full-size USB 3.0 port for thumbdrives and peripherals, a USB-C port for charging and a 3.5mm headset jack for audio -- you can buy one of three different docking stations (starting at US$150) to turn it into a fully-fledged multitasker.

Enlarge Image GIF by Sean Hollister/CNET

I'd probably skip the most expensive dock, the HP Advanced Wireless Docking Station ($289 / £233 / AU$369), though. While it allows you to literally walk up to your desk and watch your additional monitors magically spring to life as soon as you get close (the dock wirelessly pairs with the PC as soon as it's in range) I found it would sometimes forget to connect my Ethernet cable or mouse. Plus, you'll need to pay HP an extra $50 (roughly £35 or AU$65) to add the WiGig feature required to make it work.

What surprised me: the Elite x2 actually has enough muscle to make multiple screens viable. Though my configuration only had a lightweight Intel Core m5 chip inside, I didn't have any trouble running my usual mix of a dozen Chrome tabs, Slack, Evernote and Tweetdeck across three screens. It only feels marginally slower than the thinnest machines that sport beefier Core i5 processors, and our benchmarks agree.

While I'm actually a fan of the Elite x2's bundled, fabric-backed backlit keyboard (it's precise without seeming overly stiff), the touchpad is one of the most finicky units I've used in the past couple of years. The pointer's accurate enough when it works, but sometimes it completely failed to detect my finger -- or thought I was trying to pinch to zoom instead of scrolling up and down. I found myself using the touchscreen for most of my scrolling.

The Elite x2 also comes bundled with a free, battery-powered Wacom stylus in every box. I'm not much of a stylus user, but the pen feels similar to other Wacom styli I've tried: it's accurate, but it lags behind your motions. Can't complain about the price, though -- and I like how the keyboard's strong magnets double as a way to stash the pen when I'm not using it.

James Martin/CNET

The couch

I'll be honest: after a couple of meetings away from the charger and a long commute home on the train, my Elite x2 is usually on its last legs. I get between 3.5 and 4.5 hours of real-world battery life on a charge, which pales in comparison to an iPad but isn't terrible for a Windows tablet this thin.

For context, I'm also seeing around 7 hours, 17 minutes in our standard battery drain test, about 45 minutes more than we got from the Surface Pro 4. That might be long enough for a cross-country flight...but I'd rather have a thicker PC that lasts a full day online.

Once it's charged up again, though, the Elite x2 makes for a pretty decent couch surfing machine. It was light enough to pick up with two hands to surf the web or share funny YouTube videos with my wife sitting next to me. And while the 12-inch, 1920 x 1280-pixel resolution screen isn't nearly as high-res as today's high-end tablets, I never felt it lacking clarity. Just know that the tiny Bang & Olufsen-branded speakers are pretty weak and won't exactly blow you away, literally or figuratively.

Which tablet to buy?

By now you might be wondering: what about the consumer-oriented HP Spectre x2, which costs US$100 less for what appears to be the same machine? Personally, I'd pick the Elite every time. Here's why:

We found the Spectre's spring-loaded, button-activated kickstand confusing and difficult to open with one hand. With the Elite, you just pull it out.

You get a full-size USB 3.0 port for the thumbdrives and accessories you already own, instead of always needing to carry a dongle.

When that 3.5 to 4.5 hours of real-world battery life dips to 1 or 2 after a few years, you can actually open up the computer and replace the battery. (Or the storage.) You just need a Torx T5 screwdriver, a suction cup and some steady hands.

I'm a different case than most, though. The long train commute makes detachables difficult for me. But if you're set on a Surface-style computer and are willing to deal with a finicky trackpad, the new Elite x2 is a solid, capable PC.

Multimedia Multitasking test 3.0 Razer Blade Stealth 515 Microsoft Surface Pro 4 519 HP Elite x2 1012 588 HP EliteBook Folio G1 590 Apple MacBook (12-inch, 2016) 702 Samsung Galaxy TabPro S 856 Note: Shorter bars indicate better performance (in seconds)

Geekbench 3 (Multi-Core) Razer Blade Stealth 6874 Microsoft Surface Pro 4 6775 HP EliteBook Folio G1 6595 Apple MacBook (12-inch, 2016) 5879 HP Elite x2 1012 5760 Samsung Galaxy TabPro S 4722 Note: Longer bars indicate better performance