I just installed the Win 8 developer preview on one of my laptops. First impressions is it is pretty slick. I liked the Metro interface for quickly running apps and the browser. The overall speed was nice and as Ashley mentioned you get the regular desktop by clicking the desktop app. It was a little harder at first to find all the stuff I normally use, but after about an hour or two I had it down. One awesome service is the Azure platform where you can have online games using Microsoft's cloud.
I disliked that you can't exit apps without going to task manager, but maybe that is because it is a preview build. The IE10 browser while nice it takes the whole screen is nowhere as convenient as tabbed browsing, etc..which is why on 8 they have two browsers. On a desktop I'd never use the Metro IE10.
One odd thing is I can't login to Scirra.com on my WIndows 8 box. I tried both IE browsers and Chrome on Win 8. Odd....
Overall, I think 8 will be a hit. I wonder if Construct 2 will have an exporter for Metro apps since HTML5 is one language that can be used to build Metro apps. That would be awesome.