My thoughts (positives and negatives)
I posted this in the normal forums in Pendragon's thread as well.
I agree with everyone else that has said we have /r/leagueoflegends if we want a reddit-style discussion. I frequent reddit and I think it has a good system for a site that wants to be "the front page of the internet." However, the system has its limitations as well. I'd prefer that our forums here maintain a traditional message board format that is less focused on the most popular discussions and opinions at the time.
One thing I did like was the removal of general discussion. I think having GD be the one-stop hot spot for discussion makes things too muddled and unfocused. I like the idea of trying to spread discussion to multiple subforums. That being said, I'm a bit worried by the subforums as they stand now--some niche subforums (like player concepts or roleplaying) seem to be getting the axe, according to this list.
Honestly, I don't want the format of the league forums to change that much. I know I'm in the minority here, but I actually don't even care about customizable avatars or signatures (I think they can be distracting). I'd settle for linking our forum avatar to our in-game icon choice. I'd also like the forums to allow for more interaction between players, and to give us more room to form our own sub-communities. Don't hate me for bringing up DotA, but I used to visit playdota.com before I knew about LoL, and it was nice having the forum tools to send personal messages and keep track of other people. I'm a mainstay on the Player Concepts forum here, and having those upgraded features would improve that subforum by leaps and bounds.
So, essentially (in other words, tl;dr) I feel that the new features are good, but I don't like the format changes.