It's a mind blow. It's Win7 w/ touchscreen ability, they mess up everything you've learned so far about using the mouse, and simply adds the ability to mount an ISO.
Only if you choose to stay in Metro land. Otherwise it works more or less the same with a new skin.
The only annoying thing is some Start Menu things are a bit more annoying to get to. Control Panel? Windows Key + X to open up a menu that has it. Shut down? Windows key + I to open up the settings. Unless your power button is set to that.
I use Windows 8 as my primary. I don't see any jarring reason to go back to Windows 7. All the horrors were basically blown way out of proportion. But you know, I'm the crazy one. I actually enjoyed using Vista enough to make it my primary too.