I have BB7's on all my bikes. Two issues, both user error, formerly kept them from being great but have gotten better now that I know what I'm doing.

1. My rotors would go out of true. Mounted to the bike, they're fine, but when I loaded/unloaded the bike from the trunks and backseats of cars, I wasn't careful with my rotors and I slightly bent them (think: less than a millimeter).

2. I contaminated my brake pads. Touching the rotors all the time with oily bike shop hands got a little grease in the pad, and it sounded awful, like metal-on-metal. Now, I take the wheels off if I'm cleaning the bike so I don't get dirty water running down the frame to the rotors, and I keep my hands off them (no reason to touch them anyways), and I'm extra careful with bike grease.

All I had to do was load the bike in the car carefully, and not touch the rotors, and they work extremely well with no issues. Both of these problems cannot be addressed by an adjustment of the brake itself, which the mechanics you went to likely did.