Been using windows 8 consumer preview for roughly two months now. My opinion? I'm not buying the 15$ upgrade disk, I'll be skipping this generation like quite a few people skipped vista.
Now, if I had a laptop with a touchscreen, then I'd be all for it. But as it is now, it just feels slower. Pressing a button is damn faster than pointing a mouse somewhere and waiting for the button to be pressed to emerge.
Having said that, I like the new locked screen look, but that's about it.