For me, 5 and 6 tend to be the tipping points. 5 is on the bad side of average, 6 is on the good side, basically just ok. 7 is good, 8 is very good, 9 is pretty awesome, and 10 is near to perfect.
I don't believe in giving 0 or 11, and I only do whole numbers, no .5, as a rule.
So what about you?