Feature wise it has almost everything forum should have, and nothing extra. Its a forum, not swiss army knife + kitchen sink 2 in 1 (with discount if you buy 2 kitchen sinks) combo.
But I think there are few key things missing in it:
- With new topic marking thing it would be useful to have a function to mark forum with subforums as read from index. In vB it can be done by double clicking on folder icon. Otherwise I ether have to mark all forums as read or go inside forum, click mark as read link or two links if forum has subforums. After working with vBulletin for a while I already got used to it and miss this feature when browsing area51.
- Quick reply. It would be nice to have, but devs said it won't happen, so it won't happen
- Imagesets. Its a good idea to separate imageset from style, but I think implementation is rather poor. There is no way to make an imageset for other style than default, so I can't make a style and few imagesets for it without writing lengthy instructions for users on how to install it. But its way better than any other forum system, so no reason to complain much.
Style authors should be able to do (for example) a theme and an imageset and the user being able to install it. The system then automatically checks for existing components (you would just need to give the template name within the style.cfg file). We did this before here at area51, but within CVS this is currently broken. 
