@evildictaitor:"So I stand by my assertion that in this specific instance, based on Dr Herbie's specific example where he tried and failed to get Windows8 to power down, that the Windows8 UI objectively failed compared to Windows7."
Hmm, I'm thinking if he'd never seen a Windows machine before he wouldn't do much better on Windows 7 - it's shutdown is on an unlabelled popup menu that you access through an unlabelled orb that's normally used to launch apps.
The shutdown option in Win8 is exposed (IIRC) on the sign-in screen and the SAS screen as well as the settings menu so at one point it was directly in Herbie's face and he missed it. This doesn't sound like "discoverability" this sounds like mental muscle memory.
For contrast, here's how to turn off an iPad:
"Begin by locating the iPad's hold button. This button is on the top right-hand corner of the iPad.Press the hold button for a few seconds, until a red slider appears at the top of the screen that says "slide to power off."Slide it to the right. (If you don't want to shut it down, tap the "cancel" button at the bottom of the screen.)
You'll see a small wheel and then the screen will go dim. The iPad is now shut off."
Yeaaaaah, really discoverable, I bet users are going to abandon that in droves