Yep. I've been testing 3.1 (3.5 now) from beta 1, and I haven't noticed any serious issues.
Basically, the only bug, I reported to Mozilla is this one:
I click Bookmarks>Bookmark This Page, and "Page Bookmarked" pop-up opens correctly.
However, when I click on "Bookmarks" again to see drop-down list of my bookmarks, "Page Bookmarked" opens again, instead.
I have to click on some other menu, like "History", and slide my mouse over "Bookmarks" menu to open list of my bookmarks.