Personally I like the new forum but as with anything else, there is always something that could be better. As mentioned elsewhere, the last visit feature on the old board was good.
Highlighting the topics of threads with activity is good too but to take the highlight away the topic itself has to be clicked instead of being able to click on the last page, if there are multiple pages, to get to the end where the actual new post is located. If you click the page number first, when you go back to the list of topics, the subject it still highlighted as if not read.
EDIT
I noticed today thatt hey don't always get updated as far as highlighting to bold.