I am also one of the original UT players, but never really got into it online because I lacked a cable connection and it was a bit shallow. But with games like Counterstike, which I used to play somewhat extensively, I found that the pace was way too slow and levels always resorted to some sort of camping after one or both teams lost most of their players...it became an exercise on who could "wait it out" the longest. Although UT2K4 isn't perfect by any means (I loathe the leviathan, and people love to "whore it up" with the goliath), I love the fast pace of the game, making camping not worth the effort. The emphasis is placed on movement rather than aim.
But I still miss the original UT sniper rifle...I remember popping off heads from across the map without zooming in...now that is satisfaction!
EDIT: Ok, maybe camping is a problem...there was someone camping with an AVRIL and spider mines at a node for the entire map in arcticstronghold...he wouldn't budge, forcing an overtime game twice.