I finally got around to upgrading to Vim 7 today and although I have only played around with it a little bit thus far, I can tell you now that I absolutely love the new features that are in this release.
I can already say that I have three definite favorites out of all the new features and enhancements within Vim 7. My favorites are of course the in-line spell checking, tab page, and code completion features.
Here are some screen shots showing off these three features:
(and yes I lovingly wrote this in Vim)