There is defiinitely too much space wasted, the Avatars are especially shit. The thing is that a Forum should be used to communicate, it's not a good idea to lessen the space you have for writing just to show static pictures of a user.
There is a lot of pointless stuff, like the moving avatar thing, or that the ratings pop up when you hover over them. Most of them are so low res that it looks like complete arse.
The text on the Main forum page actually goes into the circle for "there are new posts" that looks kinda shit and should be fixed even if that is not the biggest issue here.
When I go to Profiles the font to the top (Profile Posts, Latest Activity etc.) is barely readable there seems to be a extreme "bold" effect on it.
I really do not like how some aspects of the new Forum move with my scrolling, not only the avatars but the website top is following me. What is the point of that? It's irritating.
There should also be actual boxes on the right, as it is now It is irritating for me, please consider adding Borders and boxes around the different aspects just like the old layout. (Talking about "new posts" "members online now" etc.)
Ranselknulf pointed towards the use of colors, while that is naturally not a very important thing it is part of the codex Identity and regardless of what you actually want to change because you think it's an improvement it is my opinion that the colors should be the same as they are now.
I also think round corners are kinda gay, make them hard and Edgy please.