To be honest, the whole idea of Firefox on OS4 excited the heck out of me when it was first suggested many years ago.
Today not so much, I don't even use Firefox on my PC or Mac anymore, its all about Webkit these days, and lets not forget we already have a brilliant Webkit browser in the form of OWB (and netsurf, but that's never worked on my machine for some reason). Firefox is slow, bloated, and uses up a ton of resources. Safari and Chrome and other webkit browsers out perform it by a huge margin.
For a while we were getting weekly updates to OWB, but now there haven't been any for 4 months or so, I'm praying he hasn't given up work on it. It still lacks a few things, a download manager being the most obvious.
I think we're better off putting our efforts into OWB and making it more usable, its almost thee. If Joerg (I believe his name is, excuse me if I got it wrong) hasn't got the time to work on OWB now, maybe he could open the source so others can expand on it.
Firefox would have been great 4/5 years ago, but these days I say Webkit is a much better option.