I recently dusted out my ZTE Open C, the second Firefox phone released (the first one being the Open, which is much less powerful than the Open C), and seeing as there are no over-the-air updates, I took matters in my own hands, and flashed the latest unstable Nightly build of 2.5.
Previously, my Open C was on FFOS 1.3. As a fledgeling platform, FFOS 1.3 was still in it's primitive stages and while being perfectly serviceable, it wasn't a phone I wanted to use as my main phone.
2.5 fixes all of the issues I had with 1.3, adds the missing features, such as the screen lock wallpaper which could not be changed at all in 1.3 which meant you had to look at the Firefox on a blue background everytime. Quickly gets pissant.
The Open C has a 4" screen, a 3MP camera (no flash, being a low-end mobile), 512MB of RAM and a dual-core Snapdragon 200 @ 1.2GHz. It might not seem like much RAM but remember that FFOS can run on 256MB of RAM, which is impossible for modern, resource hog Android, and can be done on WP hardware.
The camera is decent for shots on the go, but while it's not a deal breaker the lack of a flash pretty much rules it out for any kind of dim/night lighting. Video capture is 352x288 @ 15 FPS, good enough for quick capture on the go, but it definitively is no match against the likes of my Redmi Note, Dagger, Lumia 800, Moto X and such. It is on par with my Doogee Phablet.
Call quality was pretty good, had no problems hearing or being heard. The reception side has been improved drastically, I have a much stronger signal (-65dBm/5 bars) where I previously had about -90/-95 (2 bars).
Firefox works very well, pages load quickly and renders perfectly fine. I still prefer Opera, but that's force of habit, having used Opera since the ad-supported days.
The Open C has 1GB of internal storage, with 944MB available space -- yes, FFOS is very light on resources. It also takes microSD up to 32GB.
Bottom line: With the 2.5 update, FFOS has grown considerably, and while I think it will remain a niche OS, it is an interesting alternative to Droid/WP/BB. Alcatel has pledged to make FFOS hardware, and hell, even LG released a FFOS smartphone, which I may have to hunt down and import eventually.
Final thoughts: An interesting, exotic curiosity. If you are a little bit of a tinkerer and want a different experience than the mainstream OSes, give FFOS a look.
SKELETONS RIDING OSTRICHES