While it looks alot smoother than ie8 i still have a few reservations about the ui:
Tabs should be above the address bar. Most the major browsers are starting to adopt this approach. It makes no logical sense for the address bar to be above the tabs as the address bar is related to the tab you are viewing and not the entire window. Therefore it should be contained within the tab.
There's too much waisted space above the address bar. Previously the title would sit here. If they're going to only leave the title in the tab then surely going for the chrome approach of placing the tabs right at the top would fit better.
There's an over use of gradients. Stronger colours with more subtle gradients look far more appealing, such as chrome and visual studio 2010.
The back and forward buttons look terrible. They're fair too grainy.