Yeah, as long as MS keeps replacing it for free, then break-downs are a major inconvenience, but I wouldn't give up on the system. But if I was paying every time, even just $30 for shipping or whatever, I'd probably give up after the third time.
I'm sure MS and Sony include borked ones in their numbers, that's why you say "shipped". It includes anything that left your warehouse. To be fair, a lot of the broken ones probably get refurbished, but then maybe that's why some people are going through five or six - they're getting half-fixed ones in return.