There are plenty of shops I would trust to work on my BMW, but very few I trust to not hit me in the wallet when doing so! Cars Unlimited is the exception to every "stealership" and repair shop horror story. The owner, Mohammed, is incredibly knowledgeable and thorough when evaluating any issue. Looking at the itemized bills they've charged me less than I've been quoted at the dealer for parts, and the labor hours were well under the Bentley Manual number. This is an high-integrity shop!
The only downside is that the volume and quality of work they do will usually mean that the car is with them for 2-4 business days. This is literally the only 'downside'. Good things come to those who wait!
When I had my fuel pump replaced recently (the original OEM unit went out to lunch at 167,000 and 11 years - causing intermittent no-start issues) the car had a FIERCE oil leak that I had the parts to fix, but hadn't gotten around to. Mohammed didn't hold the car hostage over the issue; informing me of it and trusting me to take care of it myself when I said I would (and I since have).
Highs: Price, Quality of Work, Service, Attitude
Lows: 2-4 business days, even with parts on hand
Verdict: If you've got an off-warranty BMW there isn't a better value shop in Southeast Michigan (from my experience). I'd be surprised if there's a better value for BMW service in the Midwestern United States.