I just think a grade or pros/cons would be good. Of course tell the shop you are at that you would like their permission to grade the service and post a grade for the shop.
I would never ever want to be the cause of a business going under by posting something negative. I think you have to go back to the shop a few times in order to give a good or bad report.
Then again, I surely do not want to drive over an hour to have a bad expierence either. Customer service is what brings the customer back. JMO