I was disappointed in UT 2003 also but I think this game is much better. It runs smoother and has a new battle mode I believe, Onslaught (driving vehicles is pretty fun). You can get the game in a DVD edition where it installs from just one DVD instead of 6 CDs! the best part about that is that DVD transfer speeds are much faster than CD inaddition to not having to swap out to different media.
Compared to UT - much better graphics but 'feels' the same - a good thing. Even if you have a shoddy computer you can lower the graphics down (lowest I would recommend would be a 1GHz CPU with a GeForce 4 MX and 256MB of RAM). The game ran pretty nice with a 2GHz CPU, GeForce 4MX, and 256MB of RAM. I had to dial the graphics to normal instead of maxed out but I was able to have all the special visual effects on and still get around 30 fps.