I've been working on Boot 2 Gecko (Firefox OS) for the last 9 months now, and it has been both a completely insane project and an awesome project. Insane amount of work, awesome implementation.
Writing an OS from the ground up is no easy task. Luckily, we're not doing that. We are building on top of the linux kernel and gecko, both open source projects that have lots of effort put against them.
It is really starting to firm up now, especially after a few weeks ago when we had the feature freeze. There is still a lot to do, however, and we are going to be trying to bring in developers from other areas of the company to help fix bugs and make this thing stable.
Luckily, the development process just got a lot easier with two things that recently landed. One is that the b2g desktop nightly builds now include a build of gaia, so you can just download a nightly build, double-click, and go. The other is that the remote debugger gained the ability to load code over-the-wire as part of the debugger protocol, so the way gaia packages up apps and refers to them using app:// urls is now debuggable without nasty workarounds.
As we are ramping up newer developers to help with the project, we need clear documentation of the development process. The Gaia/Hacking page is the canonical reference for how to do absolutely everything, but it's overwhelming. To help with this, I made a series of 5 screencasts that cover the basics of using b2g desktop nightly builds, remote debugging with b2g desktop, hacking on gaia itself in b2g desktop, flashing a phone with gaia changes, and what to do if Firefox OS asks you to choose from two homescreens or if remote debugging does not show your source for your app.
As an aside, I find it hilarious that there are all these incorrect rumors about the speed and the memory of the phone, when the correct specs were actually *announced* in February. I guess people would rather speculate and spread rumors than read press releases.