UPDATE: Just a word of warning — we’re getting reports from several Mac users that 3.5 has issues with restoring sessions/tabs after exiting and reopening the browser. By issues, we mean it doesn’t work. Windows users are seemingly not affected.
UPDATE 2: If you’re having the problem mentioned above, go to Firefox > Preferences > Privacy [tab]. If “Clear history when Firefox closes” is checked, click on Settings and uncheck “Browsing History”.