So far service at BMW of Peabody has been good. Its pretty far some Sudbury but the Centennial drive location is right off the highway and might save you some hassles. I've brought my car in for an annual oil change, CBS system brake fluid change, and I had the idle control valve issue (i have an 2008) and they ordered the part and had the car back to me in a couple days. So far so good. The Centennial drive location is service only so it seems like they have put at least some emphasis on service quality.
Service may vary if you didn't buy your car from them so maybe its not a good option? Just my experience so far.