I don't know, I haven't read a ton of threads about broken XBO's yet. The day is young though - on the PS4 launch day I saw a lot of threads here talking about issues from faulty HDMI jacks to not not even turning on. By Monday we will see if Microsoft built a sturdier product, it's certainly bigger.
I just read this on Reddit. So MS tests every box before it ships it? If that's the case it would prevent a lot of bricked consoles coming to consumers. Which rises the question why Sony doesn't do something similar.
I have no idea what MS' policy is on this, but they might be just testing out a random sample, and not every Xbone shipped.