The single player is what I really want the most from this game. Many fond memories of playing the original Castle Wolfenstein.
You can tell it's the Q3 engine, but I don't care. The Q3 engine kicks ass anyways. There are many games out there based on iD software engines, and there will be more. Lets not forget that iD software has been watching over the development of this game somewhat, I'd just be happy that the game developers are concentrating on making a fun new game instead of trying to radically change everything.
CS was a mod to half-life, and now it's on store shelves. It's the game that is important.