I've already played the game to completion (one of the endings, that is). Excellent game. I didn't find the atmosphere to be as creepy as System Shock 2's (Irrational's earlier "Shock" game that they no longer own the rights to; also an excellent game if you can find a copy anymore). I didn't find the sound to be particularly impressive, but I was using only two channels.
Before purchasing a PC copy, make sure you read up on the draconion copy-protection the game uses. I had to install multiple times (it uninstalled itself at completion due to somehow thinking I had an illegitimate copy) and repeatedly attempt registration before the game would even allow me to play. There are also currently a limited number of installations before you're cut-off from automatic registration and must call Securom for a new code. If I knew about all of this before purchase, I would have held off until a patch (first-party or not) was available.