A few problems:
1) under the new forum display, the filtering of the list does not appear to be working. When I go to a different category in my forum dropdown menu (from the main nav line), the same list of topics always shows. When I hit search and enter another category (with no keywords), that too does not filter the list. So I just don't see how this comment in your post ("Instead, all forums and/categories are listed above the topic list, serving as a filter of the list.") actually works.
2) I'd like to be able to use my previous default avatar as the default avatar still - not the initials. How does one do this?
3) What dimensions are needed for the avatars now so that they fully fill the circles. The previous square dimensions no longer work; they don't fill the circles properly in many cases as stuff gets lopped off.