Carl and Chris Keefer understand BMWs unlike most "technicians." They clearly have a passion for their work. As a bonus you also get good service at a fair price, despite their birdrock location (I live in downtown, but will only have these guys work on my cars). If you you happen to have an older BMW, or a unique model/year, these may be the only guys in town to consider. Hard to find parts can usually be found here. Also, if you want to see some rare, cool cars, potentially from all over the world, just take a look around while you are there. If you need a referral for a Mercedes or Porsche mechanic, there is a guy right next door names Tony that can help.
Pros : Knowledge of problems associated with BMWs. Clearly respected in their field. Trustworthy