Sega had the PS2 version of NBA 2K3 online up and running at Sony's Gamers' Day event. Unfortunately, there seemed to be quite a bit of lag through three quarters of play, especially when bringing the ball up the court, which made it a little difficult to dribble past defenders. Even when there wasn't a substantial amount of lag visible, the timing for passes and shots seemed to be a little off, which is especially problematic when trying to drain a three or when you're down in the key, battling for a rebound.
As far as gameplay is concerned, NBA 2K3 seems pretty far along. On offense, we were able to execute alley-oops and a few of the new taunts and ball-handling moves that have been integrated into the game. Post-up moves seemed especially effective for scoring--players were able to roll off the defender, drive to the hoop, and make an easy layup. Defensively, players were stepping into passing lanes to steal the ball, forcing us to make smart passes out of the reach of any nearby defenders.
NBA 2K3 is scheduled for release on all platforms in late October.