I’ve been using it since the beta.
The only Metro apps I use are the Start Screen and PC Settings. 
I’m fine with the Start Screen and I really like the live tiles (at least in theory, because with no Metro apps installed I don’t see them). They could be a really elegant way to combine icons and desktop widgets, however, it seems that desktop applications aren’t allowed to use them (or at least none of the applications I use do yet).
Also, Metro can only ever use one screen, so if you have a multi-monitor setup like me, it’s even more pointless
Win8 desktop feels like a really minor upgrade to Win7.
The ribbon menu in Explorer and the new copy window with pause/resume are nice, but I miss Aero. I didn’t think I would, but it turns out that for me the glass effect created a greater awareness of where hidden windows were.
Also, don’t believe anyone who tells you that if your hardware worked for Win7 it will be fine in Win8. After the upgrade I lost the sound and network function from my motherboard, and both my TV tuners were unusable. No biggy for me, they were due for upgrading, but they had worked fine in Win7 64 and even had drivers available for Win8 from Windows Update (which simply did not work).
But the worst thing about Win8 is how it adds another layer of GUI idiosyncrasy (Metro) that will no doubt be with us forever.
In attempting to fix my hardware problems, I’ve had to mess around with Windows’ settings and it’s like a trip through computing history.
First you’ve got the nice post-Vista control panel GUI like System or BitLocker.
Then you’ve got the NT era GUI such as Disk Manager, where for some reason you can’t use the middle mouse wheel to navigate (I guess it was coded before that was common and nobody has bothered to fix it).
Then you’ve got those little tabbed boxes that popup from the control panel, like Advanced system settings or Folder Options, that feel like they’re from Win3.1.
Anyway, it just feels totally inconsistent, like they hired an industrial designer at some point, he looked at it, hung himself, and they decided they better not try that again.
…but all in all Win 8 is fine. 