I'm an old Quake hand (not one of the oldest, but I was there when we got Quake I running on our dinky PCs with an IPX stack), and it still makes the adrenaline flow to negotiate enemy territory using nothing but a mouse and my Nostromo N50 SpeedPad.
Far from the mad dashes of OSP (which I can only survive when stoked on caffeine), Urban Terror makes for more tactical and engrossing gameplay, especially with the new Counter-Strike-like "Bomb and Defuse" game modes. I still like to play Team Survivor (and I'll probably will have to keep playing it for a while, because not everyone has broadband to download 300+MB), but Bomb and Defuse got rid of most of those mad rushes against the opposite team.
Now I have the perfect excuse for sniping contendedly at my opponents as they try to rush me to defuse the bomb :)