A week after upgrading to SL, I accidentally logged into the guest account. After an unusual long waiting time, it took me back to the log in screen. Now I entered correctly my usual admin account only to find that everything had been reseted (just as a guest account is being reseted). I had lost my home folder, mail, bookmarks, dock and preferences, movies, itunes, iphoto. Fortunately I had a 5 day old TimeMachine backup, which helped me restore most of my lost stuff (except my movie collection, due to its large size -i had excluded it from TM backups, dammit, as well as some more recent iPhoto updates) All in all it has taken me 5-6 hours restoring everything to its previous condition and trying to recover the deleted pics from the cams memory card.And I am still experiencing some issues with Mail.app, which says it is incompatible with 10.6.1 for some unknown reasons (will have to delete and reinstall). This issue doesn't seem to be unique: http://reviews.cnet.com/8301-13727_7-10346974-263.html http://techpatio.com/2009/software/...w-mac-snow-leopard-guest-account-erased-files http://boards.ign.com/mac_general_board/b5146/185120720/p1/?5 Next time I will wait for the first major patch before I update my Mac; let some other idiots play the experimentees for Apple, before they find and fix such fatal bugs.