I do understand.
I'm using Android now, but I see immediately the appeal of the Firefox OS.
It will make "smartphoning" accessible to multitudes that simply don't have the money for a decent Android device or iPhone.
But most interesting to me is the strategy to get developers to write code that will work well on minimal hardware. Besides ensuring that it will run better on higher power hardware, I believe this is part of the solution to hardware and energy consumption woes: just make code that does the same with less. That's the way it was done a couple decades ago when even one megabyte of RAM was just unheard of...
And, looking at one comment in particular above, I don't think Mozilla has just launched Firefix OS merely hoping it will catch on. If developers can make apps "shiny" on less power, then when its installed on a handset with more hardware power, it should easily match Android and iOS.
Gasp! What? Yes, I use Android, and I really like it, but I lets all understand: competition is what will keep manufacturers trying their best. And with Android dominating 75% of the market share, Firefox OS will hopefully have that effect.
Why? Because again, lets understand: it would be hard, maybe too hard, for any company, even Uncle Google, to resist the temptation to produce whatever they like, hoping the consumers will just keep using it. Windows 8 is evidence enough of that...