3.5.5 seems pretty good on Linux. Except of course for Flash which is an abomination and not the fault of Firefox. HTML 5 and the video tag can't come soon enough.
the real-player plugin is also causing trouble. Since I got rid of that, it started working perfectly again.
Real Player has been a pain in the neck for a lonnnnng time. I never allow it on one of my machines.. (same for Nero..... but that was a long time ago and perhaps now improved... but I once had to do a fresh install of my OS to get rid of that parasite..)
Does anybody use realplayer anymore? Ha just kidding...3.5.5 has caused me trouble on one computer and no trouble on another so go figure, same thing keeps crashing. I installed the beta of 3.6 on the computer that was having a problem and nothing has happened since. Also if you want to just have firefox automatically backup your bookmarks, use Xmarks, it's nice because you just install it in firefox and where ever you go you can have your bookmarks.