I switched to Firefox 2.0 recently. Seems like without any bad consequences. Of course, all the plug-ins didn't work but the most essential ones (Tab Mix, Adblock) worked just fine. Finally some new features were introduced that I felt lack of in previous versions, especially the possibility to edit the search engines. Spell checking is quite handy also.
But still it's quite annoying that hot keys don't work in non-Latin layouts. If I need to copy a bunch of text while typing in Russian I have to press
Ctrl+Shift to switch the layout, then
Ctrl+С to copy,
Ctrl+V to paste and finally
Ctrl+Shift to continue typing. Maybe I should teach myself to use
Ctrl+Ins and
Shift+Ins as it seems like this bug is never gonna be fixed.