I'm not registered, so I'm screwed somewhere along these lines.
I would like a Buddy list. Some people like to chat with each other in matches, and I would usually bump into the same people here and there. I wouldn't know how the buddy list's would benifit when joining a server, unless there is some kind of message board keeping track of where your buddies are.
I'm not sure about the rival list. I'm very competitive, and it doesn't cut it when I'm upset, I just wouldn't bother playing thereafter. But hey...people are ludicrous enough to search in a hectic manner for their revenge.