I personally like a 5 point/star system where:
0: unplayable
1: awful
2: poor
3: average
4: good
5: excellent
You can include half points but I don't think it is appropriate to break down the scores any further. One of the reasons I like this kind of a structure is that the more fine-grained a score becomes the more people try to make a competition out of scores, and the more meaningless a lot of comparisons become.







