Absolutely solid with sometimes subtle, sometimes strong references to other games such as Fallout 3, BioShock etc
Manages to maintain immersion and fun while playing about with new FPS ideas and a little splattering of innovative design. I particularly like how this looks and feels like a Raven game, it has their core practices implimented well.
Solid soundtrack and audio with middling to good visuals (although a tad unpolished and out of date in places) make this game well worth even full retail price, one of the better FPSs this year. It uses the Unreal Engine 3, not sure if that's 3.0 or 3.5 i'm thinking the former. This is Ravens first time using the Unreal engine extensively i believe, it shows a little as they haven't quite used the engine to it's full capabilities. Some fire effects look very dodgy :S Although some scenes can also be very atmospheric and great looking also!
It was nice to see it lived up to it's marketing as well, some thought this might flop and that Raven were getting slack.