One of the primary uses of my PC is an HDMI connection to the Home Cinema TV, and Windows Media Center enhanced with Media Browser and My Channel Logos, fed with metadata from Media Center Master to provide a great, remotely viewable media library of several Tb.
It all works beautifully in W7.
W8 has bundled WMC as a separate entity for extra cash (free at the moment if you hurry), and in the process have beefed up the "security" to the point where most of the useful plugins don't work and you're stuck with the useless vanilla WMC experience.
I hate the whole Metro/Modern GUI imposition which is totally unsuited to anything bigger than a 3" phone screen, and though I've customized it back to an almost-W7 appearance by 3rd party hacks and switching the default file associations back to resize-able desktop apps instead of the ridiculous fullscreen defaults which make a mockery of the plural Window(s) trademark, I'm afraid the WMC situation is the killer app (in the bad, not the usual good sense).
I have no incentive to switch defaults to a new OS which, for me, is a step (no, several steps) backwards in usability.
I was one of the first of the early adopters in switching from Vista to W7, but that's what I expect from an upgrade; an improvement over its predecessor. To me, any minor improvements in W8 are mightily outweighed by its disadvantages, and it'll probably be the day that W7 reaches EOL that I'll switch, although by then I'm hoping that MS will have learned an expensive lesson from W8, and W9 will have come along and restored some sanity for desktop PCs with plenty of monitor real estate to spare.