I've only ever bought tubes from City Bicycles, but I've had their mechanic work on two different bikes of mine for three different issues. They're located one block away from where I work, so it's almost a no-brainer to bring the bike to them if a problem occurs during my commute.
Let me see if I can come up with a really polite, charitible way to say this...
How about: If they were located two blocks away from where I work I'd look around for another bike shop.
Seriously. They're nice guys, they seem to mean well, they try to be very helpful...but every single thing they've fixed for me has had to get subsequently re-fixed within a day or two. Brakes, wheels, & drivetrain. 0 for 3.
If you said you wanted to buy your BMC from them I probably wouldn't have an opinion. You want to buy your BMC elsewhere and just have City Bikes do the build?!?!? I'd rather enlist preschoolers to perform brain surgery. Nice, well-meaning, helpful preschoolers, of course.