Just a short list of things that are different:
1) The "report post" feature is now an icon in the lower left of each post.
2) The logo has changed - we're trying a new one out.
4) The User CP is MUCH different and better.
5) Private Message tracking is back on and working well.
6) When you "mark a forum read", it takes you back to the main forum listing, instead of back to the category.
7) We've added a spellchecker to all posts, quick replies, and PM's.
There are many more things, and I'll add to them as I think of them. In the meantime, play around.