Firefox OS is a tough project to evaluate. Mozilla’s phone operating system is meant for developing countries and first-time smartphone owners. To keep the price of the phones down, the hardware it comes on doesn’t really compare to today’s flagship phones, either. Instead of native apps, Firefox OS runs web apps written in HTML5 and JavaScript, which naturally incurs a performance penalty.

Still, it’s a fascinating project and you can’t help but feel at least a little bit of admiration for Mozilla given the audaciousness of launching a new smartphone ecosystem into a market dominated by a few incumbents.

Last week, Mozilla sent me a review unit of ZTE’s latest Firefox phone, the Open C. The phone is available through eBay in the U.S., U.K., Germany, Russia and many other European countries. In the U.S., the unlocked phone is going for $99. So far, however, it seems the interest is low, with the ZTE eBay store reporting just around 450 sold units so far.

One of the reasons even these rather low-priced phones aren’t gaining much traction in the market may be that the competition is heating up. Why, after all, would you buy a $99 Firefox OS phone when you can get a Motorola E with Android for $129 or a Lumia 520 with Microsoft’s Windows Phone OS for even less?

I asked Chris Lee, Mozilla’s director of product for Firefox OS, this question earlier this week. He argues that it will be a challenge for Android to go after the lower-cost market. In his view, because Firefox OS was designed from the ground up for low-end devices (though Mozilla has also set its sights on mid-tier devices through other partnerships with OEMs), it’s smarter about its memory footprint, for example.

Mozilla famously hopes to get a $25 smartphone into the market sometime later this year. At that price point, it won’t really have all that much competition. When it comes to $100 phones, though, it now has to compete with perfectly good Android phones that have better performance and an existing app ecosystem with native apps and games that currently outperform the Firefox model.

To make up for this app gap, Lee and his team are taking a two-pronged approach. On the one hand, they are working on getting tier-one apps on Mozilla’s platform so new users won’t be left without their Facebook, Twitter and YouTube apps (all of which are available already). On the other hand, though, Mozilla is also focusing on getting hyper-local apps on board for the countries where Firefox OS is already available.

At the same time, the team is also working on getting more games on the platform, which means — because of the focus on open standards — WebGL-based games for the most part. Thanks to Mozilla’s work on Emscripten and asm.js, it’s possible to write pretty advanced games for these devices. But even with asm.js, modern games still incur a performance penalty on the web platform.

As much as I support Mozilla’s mission, though, I worry about Firefox OS’s viability in the market. The Open C is actually a nice phone. It feels pretty solid, has a decently fast processor that makes the OS feel much more fluid than earlier models and a decent 4-inch screen with a 233ppi. But while it has a camera on the back, the pictures it takes are nothing to Instagram home about. The camera can handle daylight shots just fine, but everything else is a challenge.

Of course, U.S.-based tech writers aren’t the target market for this device and maybe it’s not fair to judge it by the same standards as other devices. But the Android OEMs are also aware of the market opportunity around low-cost devices, and they are already giving Mozilla some heavy competition before it can really establish itself in the market.