Don't you think that the 360 / PS3 have drawn this same attention? Those updates where there are no noticeable changes and MS is tight-lipped on the details? That's them taking care of shit that was found, both security and stability. The core that the new Windows "brand" is built around has been designed from the start to run on lots of hardware and be as closed as necessary (see WinRT or WP8). They've built a very solid ecosystem and whether people believe it or not, MS are very good at software and have only gotten better. The shared core should, in theory, make it easier on developers to make multi-platform (PC/NextBox/Mobile/etc) apps/games with much less effort while taking advantage of the hardware available. I've not developed for these platforms yet myself, though, so take this at face value.
EDIT: uhas'd. Fuckin' slow ass work internet strikes again.