As far as an FPS game goes, this is tops. We all know Epic Games and Midway Games developed a whole new game engine for this game, the Unreal 3 engine. Putting that aside, the gameplay has changed greatly over the previous Unreal Tournament 2004. Body armor no longer covers your entire body, but instead you must pick up each piece to complete the set. The weapons may sound the same, but have an entirely new look and feel to them. You can invite people into campaign games with you. But by far, the greatest improvement over the previous versions has got to be the vehicles.
If you have not already tried this game, I would highly recommend giving it a shot. It has truly been worth the wait.