It can be tough to pick a dealer. I had one bad experience with Scottsdale BMW over 5 years ago. But it really isn't fair to judge them based on that. When I was negotiating for my last 328i, Chapman gave me a better deal, so I went with them. I live a couple of hours north of the Valley, both dealerships are equal driving time for me from where I live.
I have had a little experience with Chapman's service department and the manager of the service department there, Doug, was outstanding.