Seeing as I tried 0.9 at work, and decided to stay with 0.8 at home cause 0.9 just didn't do it for me....
It states to uninstall all previous versions before installing the new version. So I backed up my bookmarks, removed my profile, uninstalled everything, and went ahead and deleted the directories while I was at it.
Installed 0.9.1, and had a good-ol time. Installed some extensions (undo close tab, firesomething (as per KshGoddess' suggestion), and 'all-in-one gestures' for the halibut). Its really working out pretty well... I still miss the old 'tab extensions' extension (middle clicking the tab bar did an 'undo close tab' and you can configure specitically how tabs should behave... like middle clicking = open new tab, but stay focused on the current tab). But I'm having fun with the gestures... looks like you can stay in the navigator window and be able to do all you need without hitting the tab bar or above. Neat stuff.
Anyone know what happened to 'tab extensions' or if it'll ever return???