I downloaded and tried out Firefox Mobile a few days ago and while it seems to be very useful (and actually fun to use), I discovered yesterday I was having serious battery drain issues. I had thought that I had gotten passed this, it was disturbing that the problem had returned. I was afraid that I was finally going to be required to reflash my phone. Then while Googling the issue, I stumbled upon a discussion about the Mozilla JVM runtime that gets installed as part of Firefox and it turns out that it’s not exactly perfected on the Nokia N900 yet, Functional, but it spins up the CPU in the background, using up the battery. So I un-installed it with the App Manager and I’m back to the regular Nokia browser only, which is just fine.