I have to agree with Seth. To me, the main issue that he raises is the burnout that constantly being matched against equally skilled players induces. This does not just apply to pros but to the casual gamer as well. It is important to have matches with players of varied skill for a multitude of reasons. One, being the burnout that I just mentioned in constantly having to play your best. Another being the social interaction and tutelage that occurs- think of it as a karate dojo. Novices will be paired off against more skilled opponents in order to learn from them and receive their advice. The same thing occurs amongst teammates. As someone who grew learning how to read and write in DOS and was entering high school as broadband came out, I can't count the number of times I received invaluable advice from a teammate that was more advanced that I was. There is also a sort of pecking order in that social structure that stands out as less confidant players rally around who they perceive to be a "Champion" on their team. All these things are positives that provide a healthy social gaming environment that will be missed out on in only utilizing skill-based matchmaking. I would expect that to lead to more bickering amongst teammates that only perceive their peers as equals who may not know any better than them.