They have been very well received by those who have bought them so far. On paper they look to be just about the perfect carbine. There is little doubt in my mind that my next rifle will be an XCR. My only issue with them so far is that I have heard claim that an ambi selector exists, but I have yet to see one or see a picture of one.
I got to shoot one at a suppressor shoot not long ago. It had the heavy barrel, bipod, and the can on it, so it was quite front heavy in that configuration, but that shouldn't be typical.