It looks like all they've added is the Fullscreen API. Well, it's very early for IE11 anyway, usually they add more features over the release cycle. Let's hope they add more interesting stuff over the next few previews.
I really doubt they will add all that much. It's really simple. MS does not want compatibility. They don't have interest in it. They want to isolate user familiarity and feature so that comfortable users won't use other browsers.