There a lot of things I dislike about v5. (wasn't around for any other version really, the tail end of v4 maybe but I can't remember that far back beyond having no clue what I was doing)
1. I wasn't a fan of the shoutbox once I realized no one was using the forum itself. Once I made that go away, the forum was used as it was intended.
2. The calendar was seldom used at all so after a while, that too had to go away.
3. The news feed was simply annoying. I can think of other ways to broadcast what little fits on the newsfeed. It too had to go away.
4. The Legend on the home page. Seems really useless. Most know when something is new and when something is not. It's a space waster. I tend to make it disappear on most of my themes.
4. Participated being available in two places seems odd even if one can be turned off in a user's profile. (I was making the one on the nav tree disappear on most of my themes regardless of it being able to be turned off but will probably put it back for those who want it)
5. Forum Information & Statistics is just too balky. Taking up so much space makes it stand out way too much.