To me, the two biggest knocks right now is the lack of a social forum that everyone can access, and nothing resembling the Active Topics option we had on the old board.
The former I think hinders both old and new users. Look, I get it; the way it's set up is to cordon off the political threads, because the board as it exists now is a commodity the owners are trying to make money off of, and, bottom line an overly Left-leaning sports message board isn't exactly a recipe for success along those lines. That sucks, and, quite frankly (IMO), the type of advertisers or users that are scared off by such a thing aren't worth any kind of effort in the first place, but that's not my call.
But sectioning off ALL of the social threads, so that there's no music or movie or TV or ANY non-sports/board discussion just seems really bizarre and shortsighted.
And as for Active Forums, yeah, that's totally a preference thing, but I'd pretty confidently bet that's how most of the legacy users were navigating the old board. That's not say that has to be the only option; more navigation choices makes sense, but I think not really having any option that works like Active Topics isn't great in terms of retaining or drawing back old members. The whole "show unread" thing just doesn't work as clearly and simply and easily as Active Topics did.