Tabs, huzzah!
Interesting side note to this: I was alerted to this release when I got an e-mail from the UserVoice site saying my upvote for the Tabs feature was released because the feature was now done. I have to say, the widespread adoption of UserVoice has been one of my favorite things about the so-called "New Microsoft". I've had multiple UserVoice suggestions on different products actually implemented; it seems to be the first bug/feature suggestion box from a megacorp where there's a sense that people are actually paying attention. Please tell any teams at Microsoft not yet using UserVoice to do it!