well i have now had a few online games, first on normal then on expert a couple of times (yet to complete subway on expert) but yeah, its a good game and everything but i dont think its the type of game for me. i guess im just not into all zombies and everything. other than that, i think the gameplay and the features are great, and it is quite a bit of fun when stuff gets tense.
i will probably be unistalling the demo sometime soon.
EDIT: by the way, runs smooth as butter on my system (see sig) and its hardly the latest and greatest. runs better than tf2 and thats on all high/very high, 4xaa/4xaf, 1440x900. doesnt look half bad for the source engine and to be honest i was expecting a lot worse - well done valve.