Tonight, as I watched the Warriors game, I tried out three different internet live gamecasts.
NBA.com sucked. Game updates lagged 10-15 minutes. If you aren't watching the game live, maybe this site is okay for you.
Espn sucked less. Games updates, AFAICT, uses polling against cached data sets. What does that mean for you? Data can be from 0-10 minutes behind. Better than NBA.com, but far from ideal.
Cbssportsline.com, luckily, is awesome! Updates are nearly live. This is the way to go if you are following a televised game.