i have a 56k and i can play jk multiplayer with barely any lag- if theres 4 people or less and other people have cable/dsl or a fast 56k connection(relatively anyway).
sometimes its really bad, but as long as i have a good host i can play with very very little lag. i like playing sbx with trails and it works fine! then again, i've had some lag on my lan too(!?).
some ppl say q3 netcode is far better, but maybe its not as good for saber fighting? hopefully it'll run well, and hopefully raven tweaked it to be more able to handle sabers? maybe i don't know what i'm talking about.
btw, my ping is usually 190-350