I have only been using the new forums for a few minutes now but right away I notice that:
1. Every single thread is marked unread.
2. The button that's supposed to take me to the first unread post takes me to older posts from many weeks ago. Only after I re-read the last page it will work properly next time.
3. I can't quote multiple posts anymore.
4. Posts are now referred to as "messages". I don't agree with that.
5. A member's post count and join date is no longer shown next to their name. Instead, everyone is just a "new member".
6. I prefer the old emoticons
7. Miscreant did a great job summarizing some of my other complaints
Just like with google maps, this is another example of attempting to improve something that worked well enough in the first place, only to introduce more problems than it fixes. The only thing that needed fixing was the lousy search feature, but I haven't tested it yet to see if anything has improved. There are some new features that I like, but further refinement is necessary.