Matchmaking is the generic term for all games where you pair up with specific users and play with them. Anyways, I feel the matchmaking system will be awesome. Having matchmaking running in the background without you even knowing is a pretty neat feature. If you decide you want to play multiplayer for that specific game, chances are, the match will already be found with users similar to you. How they act, how they play are two key factors to the new matchmaking system.
As for speed, they recently upped their hardware by 53 MHz I believe. That's a pretty nice upgrade, but for overheating issues, not so great. They confirmed that the Xbox One will pretty much run 10 years without any problems, so I don't think having a decent overclock on their GPU will do much harm. It does increase the chances of overheating and RROD problems, but just by a little percentage. Graphics-wise, I haven't heard much information from that. All I know is that they're saying it's somehow better than the PS4 since it gives a sense of realism when playing Watch Dogs. The two consoles will probably be very similar in terms of graphics though, so I'm not worried about that.