Neil Turner has a review of the new stuff in Firefox 0.9. I’m waiting until it’s released before I upgrade.
djst also has some suggestions for improving the new look introduced with this release. The problem is that the new theme does not conform to the Windows XP interface guidelines, unlike the old theme (Qute). Interestingly, this brings Firefox back around to one of its original problems — when it was initially released it didn’t behave enough like a Windows application.