@Felix - This is why this feature is for security and minor releases only. We're talking a limited number of carefully considered fixes to address security issues or major bugs. We've been doing this a long time and have gotten extremely good at avoiding breaking plugins or themes (even the terribad ones).

One can enable background updates for major releases too. It's no more difficult for us to implement — but, of course, it is more difficult for us to avoid breaking sites. We aren't missing the point. This is the point right here. We know how dangerous and scary this can be, which is why we're doing this extremely carefully. We've been collecting an absolute ton of stats in 3.7, and we've also made updates much more reliable both of which are setting the stage for us to continue to improve the stability of updates. Not just the update process, or the ability to detect actual compatibility issues or failures, but approaching WordPress development in such a way that we can continue to keep plugin conflicts to a minimum.

We also have the ability to roll out an automatic update slowly. Assuming 3.7.1 isn't a pressing security release, we'll be able to release it, wait 48 hours, then release it 1% of installs (let's say), then slowly increase that percentage for a day or two, specifically watching for failures, support requests, and the like.

And yes, updates do fail, even if you've never run into one. Even if 99.9% succeed, that's still tens or hundreds of thousands of sites. Which means we have no choice but to be perfect.