We've had okay experience with BMW of Bellevue. They've been very generous with CPO warrany repairs and always communicate well. car is mostly stock but has supension/exhaust and they don't seem to give a crap about mods as far as I can tell.
only bad experience: they washed the car (our mistake for not telling them not to) and got some kind of cleaner overspray on one of the DPEs. The polished aluminum didn't take kindly to it. Took it back, and they "fixed" it by doing some kind of acid wash down of the whole wheel. It stripped the cleaner residue, but holy crap it did a number on the aluminum and the DPE center cap.
We're going to re-polish the wheel by hand and hope it comes back to life/luster. Center cap is toast though.