The movement is different, it's not as much fun with regular weapons, but it makes instagib more fun IMO.
If I could find a copy of UT2K4 that'd be great. Can't seem to find a copy of it anywhere anymore, especially after UT3 came out.
UT2K4 has 5-6 CD's total. If you can find the Editors Choice edition, get it. It comes with all the updates and content packs ever released. best of all? a single DVD.