Ever played it? If you haven't, try one of the free weekends...there's another one coming up soon to celebrate the Soldier update.
It's just a well-made game. Despite the fact that I generally don't like first person shooters very much (with the exception of really good ones, such as Wolfenstein 3D and Unreal Tournament/UT2004) I liked the game. Not enough to pay 30 dollars for it, but still.