I've actually set 8 as my default over 7.....
It's such an interesting system, two interfaces in one and come together to hybridize. I think it works fine with keyboard and mouse. I got my wish with scrolling through the Start Screen and not just tapping on page down or page up keys.
As since it's an alpha build, of course there is some weirdness with it. My stickler is the lack of hot-swapping hard drives. I can't get a hard drive plugged in without shutting down, plugging the drive in, boot up and restart so the system sees the hardware change. That is annoying....
Also, the placement of some popup Metro boxes are just queer. The time part of the Charms bar, what?! It's slightly over the Taskbar, it's over the nav bar in Immersive IE10, it's just awkward! Anyways....