So I read your post in fear, backed up via MozBackup, and then upgraded to see what would happen.
Luckily I had none of the problems you did - except the font rendering has changed. This seems to be a global thing - tab titles look a little different (I think), but most notably almost every page I go to looks a little off - like the fonts aren't being smoothed properly, or something.
Super noticable on text heavy sites (like Gmail and Slashdot).
After the usual amount of fucking around trying to find what it was, I found some 'cleartype' settings (about:config, search for cleartype) that were non-default, so I just right-clicked them and reset them to default, and now it is back to normal. YMMV.
As is usual with every Firefox update, may the force be with you and your plugins at this stressful time.