Are you talking CMVAP arbitration? My experience with it was that the GM service people on the phone became very hostile and accused me of seeking arbitration because I wanted out of the lease. I did not proceed with arbitration as a sign of good faith, but the car was still never fixed to my satisfaction. It was a 2001 Sunfire GT that had loud front end thunking noises when braking. The repair attempts were a comedy of errors spanning over 8 months and at least 7 service visits. Ultimately their response was "that's probably as good as it gets".