We have mixed reactions to this emphasis on web apps. The philosophy lets developers quickly port apps to Firefox OS, and lets phone makers include a lot of apps that aren't always available beyond major platforms. Our test unit shipped with third-party apps like AccuWeather, Facebook, Nokia's Here Maps, Twitter, Wikipedia and YouTube. However, this can be frustrating when you realize that most existing Firefox OS apps aren't much more capable than a mobile-optimized website. Here Maps can cache an area you're looking at for offline use, as it can elsewhere, but you can't jump over to Here Drive (like on Windows Phone) to get turn-by-turn navigation. Accordingly, you tend to lose major functionality present in native apps on other platforms, like most forms of push notifications and inter-app communication. Mozilla tells us that cross-app support is rolling out, and that app notifications will come in the OS' 1.2 upgrade; still, it may be a while before we get Firefox OS software that feels completely at home in the modern smartphone world.

It's difficult to realize exactly what you're missing, as there aren't many apps in the Firefox Marketplace, Mozilla's official store. While that's somewhat forgivable given the web push and Firefox OS' limited market presence, it also leaves us hard-pressed to find the big-name apps that we like. Right now, many Firefox OS programs are filling holes left by better-known titles: Check-In Fox replaces Foursquare, for example, while Sketchbook Squad substitutes for Doodle Jump. We have noticed major releases like Pulse and SoundCloud, but they're in the minority. Discovery is limited to finding the newest or most popular apps in a given category. Although Firefox Marketplace will undoubtedly grow in the months ahead, it currently doesn't hold a candle to mature app portals like the App Store, Google Play or the Windows Phone Store.

The OS itself is equally young. The Open unit we received is running a pre-release version of Firefox OS 1.1, which introduces surprisingly basic features like MMS and a search option in the music app. The phones on the market as of this writing are still using 1.0.1, and there's no word on whether or not they'll get 1.1 or later. Mozilla says that it can push security fixes itself -- an important advantage over some platforms -- but that bigger updates will usually require carrier or manufacturer approval. Regardless of the OS version, many of the stock apps include only the bare essentials. You can't put a video on repeat, for instance, and media syncing is limited to copying files in USB mass storage mode. Concepts like NFC and voice recognition just don't exist in Firefox OS at this stage, and there's no guarantee that they will, given the focus on low-cost, open technology. Firefox OS may be a great introduction to smartphones, but it's limiting for seasoned users.

Performance and battery life

Gauging the Open's performance is far trickier than it is with other devices. It's not just that we're looking at our first Firefox OS device, which prevents many direct comparisons; it's also that there are very few benchmarking tools. Still, there's enough here to give a clear indication of how well ZTE's handset deals with common tasks.

Mozilla needs more capable hardware to demonstrate Firefox OS' potential.

Getting around the OS is smooth enough. Although the Open is running on just a 1GHz, single-core Snapdragon MSM7225A and 256MB of RAM, the home screen, browser and many apps are mostly stutter-free. The hardware could keep up with a few 2D action games, too. Just don't expect a media powerhouse. We couldn't play H.264-encoded 720p video, and there aren't yet 3D games available (though WebGL makes these possible).

More importantly, browsing -- Firefox OS' very reason for being -- falls a bit short. Everyday web surfing is fine, but more sophisticated pages and web apps either take a while to load or periodically bog down. That subjective experience is supported by our web benchmarking. The Open took 3,665ms to complete the SunSpider JavaScript test, or more than twice as long as the Lumia 520 (1,400ms). It's more comparable to the 2009-era Motorola Milestone, better known as the GSM equivalent to the Droid; it wasn't much slower at 4,628ms. We tried other web tests to play it safe, and the results were less than flattering. Kraken, Mozilla's own JavaScript benchmark, took 67,371ms to complete where a Moto X we have on hand (admittedly, well beyond the Open's league) can finish that same test in 9,295ms. Google's Octane wouldn't even run on the Open -- it took several tries just to reach the page without an error, and the phone would invariably give up partway through.

Cellular data is also an issue. We're not concerned about the Open's modest HSPA speeds, which on Canada's Telus network averaged about 3.1 Mbps for downloads and 1.3 Mbps for uploads. It's the reception that sours the experience. The Open is very sensitive to signal changes, and it's considerably more likely to drop its data link (at least in Ottawa) where other devices using the same 3G service work properly. When a phone that absolutely needs a good internet connection has trouble sustaining that connection, there's a serious problem.

Battery life, on the other hand, is superb. Whatever gripes we might have with the basic software feature set, it keeps the Open running for a long time on a small lithium-ion pack. We couldn't run our usual looping video test, but it was easy to last through a day of moderate-to-heavy use that included several checks of both Facebook and Twitter, a similar amount of browsing, a 20-minute call, 20 photos and two short videos. Based on less-strenuous use after our formal testing, we could see the Open lasting for two or even three days without a fresh charge.

Call quality is also good. In reasonably quiet situations, both ends of the call are loud and generally quite clear. There's no noise-canceling microphone, though, so you'll have to shout if you're in a loud environment. The rear speaker puts out sound at moderate volumes, and it isn't anything to write home about.

Wrap-up

We should reiterate what we said earlier in the review: the ZTE Open is partly intended as a developer phone. For those customers, it does the job well. You don't need a quad-core processor or a 1080p display to demonstrate that your HTML5 app runs properly. For $80 unlocked, the smartphone is even something of a bargain; it's cheap enough that you could buy several for a programming team. If you're looking for a testbed device, don't hesitate to pick one up.

There are also certain everyday customers who might like the Open. If you're just considering a smartphone for the first time and object to the complexity or cost of what's on the market, it's hard to beat the pricing. On Movistar Spain, the Open costs €58 ($78) with prepaid service; the Optimus L3 II is twice as expensive, at €116 ($156). Travel to Colombia and the 149,900 pesos (also $78) that you'll pay at Movistar will easily undercut a phone like Samsung's Galaxy Young, which costs 317,900 pesos ($167). Mozilla argues that Firefox OS brings smartphones to a wider audience, and it's right -- some customers would be relegated to a basic feature phone if the Open weren't available.

For many of you reading this, the Open won't make sense. The price differences between the Open and more advanced devices either won't matter as much, or aren't that large to start with. Americans will want to look at the Nokia Lumia 620 from Aio Wireless -- it's only slightly more expensive at $100 prepaid, but much more powerful. If you can spend $30 more beyond that, you may also want to consider a few Samsung phones, such as the Galaxy Amp (at Aio Wireless) and Galaxy Reverb (at Virgin Mobile). It's a tougher call if you're in Spain or another market where these deals aren't available, but we would investigate phones like the Optimus L3 II or Sony Xperia E. The Open is fine as a child's first phone or a backup device, however.

Whether or not the Open fits your needs, one thing is clear: Mozilla needs more capable hardware to demonstrate Firefox OS' potential. The Open is good for someone whose alternative would be a basic flip phone, but the camera quality, connectivity, display and performance don't do full justice to the software. Thankfully, more smartphones are coming. Along with a more powerful ZTE phone, we can also expect the (unsanctioned) Geeksphone Peak+. The as-yet-unannounced devices from Huawei and LG may also be worth waiting for. Firefox OS could easily take off -- it just needs a better launch vehicle.