Played around with Windows 8 on my slate. As it has only a Wacom type touch screen (i.e. pen input) and is also a bit underpowered, it's a bit rough going - and they still have to work on the UI, some things are disingenuous - I mean, I understand that this is a new paradigm, but still...

Gripe nr. 1: Save for settings and desktop, no apps would open. Discovered that the minimum resolution for apps is 1024x768, the resolution after install was set to 800x600, though.
Gripe nr. 2: There's no fast way (for me, at least) to close an app. I have to move the pen to the upper screen border, drag down to the middle and then to the complete left. Then I'm seeing just the green Metro background, another tap/click brings me back to the app overview.
Gripe nr. 3: No sliding through the app overview for me, unless I use the scroll buttons
Nr. 4: Where's the shutdown? Oh, it's hidden in "settings => power"
Nr. 5: If you go to the desktop, the start button will not give you a menu but will take you back to Metro. Accessing your programs has to be done by getting the Search pane (pulled from right screen border), tap on "apps". What's nice though: The programs and apps are sorted alphabetically if you want a complete overview.
Nr. 6: If some application pops up the virtual keyboard I didn't see an easy way to fold it in again.

Summary: Not ready for prime time, yet. Though I do like the "Reset Windows" option - no more reinstalling!