I have two concerns about Windows 8.
First, and by far the biggest, we all know the crap Microsoft pulls with the Xbox, they are doing that right now, for the whole world to see. I don't see how anybody can possibly honestly believe that this couldn't be the start of a slippery slope towards pulling the exact same crap on desktop PC's. It's not as if this is some sort of made up fiction by fear mongers, it's for real, Xbox Marketplace.
What's to stop MS from making Windows 9 (whenever it happens) into a desktop version of current xbox software? turning the vast majority of home PC's into closed off systems, or even worse, progressing that way with Windows 8 service packs? Personally I'd rather vote no with my wallet now, and refuse my paltry $40 to MS, before that happens.
Second, Why oh why are Microsoft forcing a touch/tablet OS on people? You can easily see that their share of the smartphone/tablet market is next to nothing. Xune was a failure, Windows Phone was a failure, Surface may look shiny and interesting, but why believe it will fare any better than previous offerings. The whole setup stinks of the beginnings of forcing it's way into a market share. What good are your Galaxy Tabs, or iPad's when the vast majority are using a Windows desktop that only the Surface will be capable of interacting with? So long other manufacturers being able to synch tablets and phones with desktops, MS could be on the path to locking them out for good.
OT: Do desktop users need it? Dunno. Personally I'll stick with 7, doing the job nicely.