1) the thunder +/- units back a few years ago were not good but you could see where it was going watching the play...

2) even though you are a step removed from letting the +/- of an individual be determined by the effectiveness of his teammates....you still have to contend with who they're facing as opponents, differences in possessions depending on when people get in the game, and then dwindling sample sizes. it doesn't seem to me to be any different than slapping a number on "did you see them go on that run at the end of the half?"

it may be that there is some highly awesome math going on behind this that i haven't considered but +/- doesn't seem to me like doing more than micromanaging a scoreboard.