I've spent a far bit of time using Windows 8 over the last day, on both a touch interface and with a mouse and keyboard.
The Touch interface is wonderful and really flows and works well for me.
However, I do like the mouse/keyboard interface too. It works, feels natural to me. There are a few annoyances that I'm sure will be ironed out before they get to the beta. I'm running this in a VM so I'm not getting the best experience.
It would be nice if you moved your mouse pointer to either edge of the screen, if the start screen then scrolled in that direction, rather than having use the scroll wheel or scrollbar.
Being able to hold the left mouse button down and drag to scroll the start menu would be cool too. (Works well in Civilisation anyway)
Easier access to the shutdown button would be nice too.
Some kind of keyboard shortcut pop-up list would be nice, make it easier to learn my way around with just a keyboard.