I have a couple of mates who are reporting problems. One cannot even get the game to run properly on a pretty decent setup.
Maybe it is just luck, but I have had no problems at all.
The voip is screwed and the game browser is a little buggy but the rest of it I am loving.
What's up with the Voice chat?
I've only played 3 games in 1 on 1 with a mate over the net but it worked fine - just strange how it pulls the push-to-talk key from your Steam chat settings.