Hello,
This is probably a minor note, but one feature of some recent tabbed interfaces (Chrome) that I quite like is deferring the auto-resize of tabs after one is closed until either a delay or the mouse leaves the tab area. This makes subsequent actions (either selection or further closes) more pleasant, because you don't have moving targets, which can cause accidental actions.
Pretty low priority, obviously, but I thought I would bring it up because I've been opening and closing lots of tabs today.
-MinRK