I think any dealership you go to is going to have horror stories.
Personally, I've had a great experience with Dreyer & Reinbold. I purchased a CPO 328xi coupe in MA, but have had it serviced at Dreyer under the service plan. The service rep I have been dealing with there (Eddie) is fantastic. I found him to be honest, as well as an attentive listener when it came to addressing specific questions or concerns. I honestly expected that when taking a 4 year old BMW into the dealership to be "inspected", they would return with a list of several thousand dollars worth of work that "needed" to be performed. I was pleasantly surprised to find myself in the wrong.
All fluids changed/flushed, inspected, serviced, seatbelt extender arm replaced under CPO warranty, and headlamps realigned... I walked out after happily paying $66.00.
I was given a clean 2012 535xi loaner car to drive, and I had my car back within about 4 hours. They also emailed me a complete online interactive report of the findings on my vehicle.
While there are some things I will certainly not take to the dealer because of their unnecessarily high rates (i.e. oil changes after my service warranty period expires next year), I was still completely satisfied with my visit.
Your mileage may vary.