to compare UT2k4 onslaught to Halo. It feels a little like the larger maps in Halo w/ vehicles but sped up like a flashy arcade game. I'm going to preorder this game, good fun.
I think the speed doesn't allow for as much depth in gameplay as Halo does though. Or realsim, or teamplay tactics. You won't see people pull off impressive moves as often because of the simplified deathmatch mechanics(in whatever mode). Does that sound biased? Sure, but everyone plays the same in UT2k4 where as with Halo you remember even the slightly above average onscreen names because they have distinct personalities in game.
Not that Bungie couldn't learn a thing or two from Epic about games. Or that either one of them needs to learn from the other. I just might prefer it if they did.