Best multi-player game I have ever played. It improves on the original in so many ways.
Graphics: Since the game uses the Source engine the graphics are great.
Sound: The sound is great you need it in order to really play. Someone may be sneaking up on you and you hear there footsteps and you turn around and HEAD SHOT!
The best thing about this game is that there is so many custom maps you can never really get bored with it. The multi player teamwork is really great too. You can go back to this game over and over again. I've been playing it for about a year and a half and I still play it.