Well...
It would up your performance no doubt, but I wouldn't anticipate becoming the ultimate UT player, well, I don't know how you play, you could be really really really good.
I played the Q3A demo on the net, the lag was pretty bad so I only play against bots.
I played Quake 1 on the college network once, it lagged pretty bad, but I could still turn when it froze, allowing deadly accurate shots, caned 'em. (Don't know how lag effected the two I was against, they might not have been able to turn when it lagged, which would explain my victory)
I'm not the best Quake player around, but I can generally beat anyone in the college course I'm doing.