No problem here...yet
Our XLR is now 3 months old and has about 2500 miles. No squeal yet.
I will admit to not having been very agressive on the brakes, but regardless, there should be no squealing at the mileages you guys are talking about.
My '02 Mercedes ML-500 had a similar problem at 13,000 miles. New model, brand new brake design. I took the vehicle to Brake Check and "independently" verified the rotors. They were in spec. No glazing. We checked the thickness of the brake pad. Again, in spec.
The problem was the brake pad compound. Without good 'ol asbestos, the first compound used by Mercedes caused the kind of squealing you guys are describing. M-B did have a new formulation out fairly quickly.
M-B put new pads on gratis, after a round of loud complaining by me. I have 45,000 miles now, and haven't heard a whimper. I suspect the problem you are experiencing is of similar origin.
After reading your comments and the link to the other thread, I admit this is a cause for concern. I will be listening.
aviator :cool