Having watched one of the best HS leagues in the nation play for a few years I'll tell you that although 90 may have an off day, any pitcher who can consistently throw 90 down the middle will be very successful. Even in a good HS lineup there will typically only be 2 or 3 hitters who can actually handle 90. I remember the kids from our school telling me how they could handle Robert Stock when he was a sophmore because he just threw it down the middle. Then I looked at the stats. They didn't handle Robert Stock.
There are also major league pitchers who don't have great control but just plain throw hard/have great stuff. Schlereth would be an example.