The core of the game is as strong as ever but everything surrounding it this time out is a bit lacking.
The Maps: Seem to have been designed by people who have never played a game like this before in their lives. They LOOK very nice, and most exhibit interesting aesthetic flair but when it comes right down to it, that does absolutely nothing toward make them good arenas for combat. Their quantity is also a bit lacking (especially given how few are actually good), even with the post-release "booster" packs.
The Game Modes: Are... horrible? UT has always been the franchise for having interesting and fun game modes but I have to say they really dropped the ball here. It's almost as if they weren't even trying. Onslaught, Assault, Bombing Run, Domination... where are you?! I don't understand why you would lose so many game modes from one installment to the next.
The new "Warfare" mode seems to have been the focus of this outing (especially since there are so many maps for it) but, frankly, it just doesn't really mesh with the Unreal experience and seems to be attempting to take it into the realm of Battlefield. I know everyone loves drivable vehicles and all that but... come on, this is Unreal, why are we making it something its not? Of all the new game modes, I think Greed is perhaps the only one which actually succeeds at being enjoyable.
Either way, its easy to see why so many people still play UT2k4 -- it simply offers more than this; a larger variety of quality maps, far more enjoyable game modes and a generally more complete experience.