I use a release build (currently v10) from romaxa and it doesn't do this. Firefox Sync (if you use it) at startup does guzzle a bit of CPU, but once that's done, it's happy. I'd like to know if Nokia are doing their own platform UI, given that Mozilla are soon to drop support for the current cross-platform (slow) XUL UI in favour of just Android. Also, I assume a corresponding AIR runtime will be nowhere to be found, which would be a shame given it might enable another avenue to get some pre-existing apps onto the platform.