Before this explodes into a huge battle like threads such as this have tended to become in the past, let me give my two cents.
First off BBB08, congrats to your son for a very successful showing at the tournaments and for his college commitment. With the information given, it is obvious that he is very talented and has a future in baseball. I don't view your post as badmouthing PG in any way, which I think some people might and that could cause some misguided reactions. I do, however, feel that you might be putting things into a somewhat skewed perspective.
PG evaluates talent very similar to how professional scouts evaluate talent. They have many players at their events and try to give their own evaluation of the player at the time the player is being seen. However, one must understand that a PG grade is a scout's opinion. Just because someone received a specific grade from PG does not mean that the grade they received is what they are destined for in the baseball world. In fact, often times there have been players who have succeeded the grade that PG gave them (PG has openly admitted that they underrated Prince Fielder when he was in high school...
http://www.perfectgame.org/Art...ew.aspx?article=5137 . Another example would be Tony Sanchez, who went to Boston College and was drafted 4th overall by the Pirates last year...
http://www.perfectgame.org/Pla...rofile.aspx?ID=17491 ). The opinions of the people involved with PG are generally very well respected because these people are very well respected within the baseball world. But let's not forget that they are opinions and not set in stone.
A player that receives a grade of an 8.5 means that a player is in between an 8 and a 9. The definition of a player with an 8: potential mid round pick, definite DI prospect. The definition of a player with a 9: potential top 10 round pick, top DI prospect.
With respect to your son, BBB08, I don't see PG's evaluation being that far from the truth. I obviously can't comment on your son's actual skill level because I've never seen him play, but an 8.5 rating is no slouch. It's evident to me that he is very talented and has had success. I wouldn't worry too much about the ratings that he receives, just keep on throwing and let others worry about grading him out.