@ mdmd: The update process for Vista/7/8 is the same, but dont confuse that with the upgrade. 8 has fewer editions, a new licensing scheme (Sytem Builder, upgrade-only, Windows Media Center sold separately instead of being free, etc.). And it looks like they also have a new (not entirely, but still different) activation method.
From what I've heard there was an upcoming SP2 for 7 as of early last yr, but MS supposedly cancelled it in favor of promoting 8. Maybe I'm wrong, but I dont think a new SP is coming for 7, although they will continue to update it regularly until the end of its' supported lifecycle, which is still far off (XP ends next yr I think, Vista not too long afterwards).
I'm not sure if MS "must" update/upgrade Metro apps, maybe you can elaborate on your opinion? I suppose if you paid for an app then they're legally obligated to support it, but probably not if it's free. Also, some apps are made by 3rd-party developers/publishers, so it would be their responsibility to support their app, not MS. Of course, you can just uninstall an app if you dont like it, and it wont receive updates. I keep only a few apps on my Start screen, the rest are removed. Everything else is just shortcuts to my most commonly used desktop programs, all grouped into relevant categories. I'm starting to love it more and more because I can just press the Windows key and start typing the name of any app/program I dont have pinned, and it will usually come up near-instantly.