I've been playing it on my home network, me and two other computers with only a few problems... the main problem comes from running the game with extra bits installed... I went down to a basic .ini file with only the necessary serverpackages to play u4e, and it flies beautifully... CTF levels work the best, as they are generally large enough, and easily navigated, but domination levels do good too...
dunno... I never did get around to playing Invasion.
since I got Gauntlet working on the network, I haven't played 2k3 at all... I'm just having too much fun