I have to say that I'm totally digging PES 2008. I was a bit apprehensive to begin with, but after installing Kitserver and the latest beta drivers for my 8800 GTS card, it's running incredibly smooth. I haven't tried online that much, waiting a couple of weeks for it to be sorted out.
With regards to gameplay, I really have few complaints. Sure, sometimes strange things happen, but imo it plays a lot better than PES6 - I would never be able to go back to that now. I've been playing the series since ISS on PS1, and I truly feel the game has gotten better with each revision and this time it's no different.
Granted, it feels like a rushed release and the music is just plain ridiculous (K-k-k-k-kick it!), but be glad that you're playing it on the pc, and send some love to the people responsible for Kitserver and all future patches.
-Schack