While it is a great game, it at times just doesn't feel right with out a mouse and keyboard.
First off, the essence of UT is multiplayer, it began mostly as a multiplayer game and it remains that way. If you want to get your full moneys worth out of the game, you're gonna want to have an Xbox Live connection. If not, you aren't stuck in the mud, you can play the game with offline bots, but honestly its just not the same. Match variants range from death match, team death match, CTF, and other objective based game types. The action is frantic and a lot faster than games like Halo 3 or Call of Duty 4. Another big part of the game is the weapons. You have a big variety of weapons here, and to add on to the fun each weapon has a second fire. While you'll have standards like rocket launchers, your classic shot guns and assault rifles have been given a big scifi twist. Knowing how to use each gun properly and efficiently will give you a big edge up on the competition.
UTIII does feature a single player mode. I've questioned why exactly it does, but whatever it's there. The single player mode is a story of... nothing that really matters. When it boils down to it the story is crappy and the single player is nothing but pre set instant action games with bots. The good thing is that you can go through them with your friends on co op to tone your skills. But unless you really want the achievements, you'll be spending most of your time in multiplayer.
Look wise, it's very Gears like and the reasons to that are... very obvious. So much so I don't even have to say anything more. Epic knows how to use their engine but other companies can manipulate it to looking different than Gears, but the way Epic uses it and it's architecture the two games look eerily similar in comparison together. UTIII is a fantastic looking game but I feel they could of made it look not as Gears like as it is.
I mentioned control issues earlier. Lets be straight, there are no real control issues, this is just a matter of preference. UT is like FPS on crack. It's a very ADD twitchy game where speed and precision is needed. Trust me when I say that it feels a lot better with a mouse and keyboard. That's not to alienate anyone since you can get by perfectly fine with the controller especially if you're not used to PC games. Another little gripe is weapon switching when you have a lot of weapons. It would be easier if the LB and RB button cycled through weapons left and right, but only one of those shoulder buttons does and the other seems to be for a hot key type use. It's a minor annoyance at most, but still is annoying.
Another thing that is a big disappointment is the lack of mods. Both the PC (Obviously) and the PS3 version have mod supports which are simple to install and easy to manage. You'd think with Epic handling Microsoft's baby franchise in the absence of Halo that they'd open up the 360 for Epic to allow mods in this version of the game.
Over all, if you want a fast paced FPS for your 360 library, UTIII will fit it. It's not a game for casual FPS players but it will do well for anyone who doesn't have a PC to run the game properly.