This definitely looks intriguing, and I'd love to give it a spin, but I think thisismynext.com sums it up pretty well- you're basically having to manage 2 OS versions on the same device. 2 control panels, 2 ie versions, etc. Oh, and you're running full desktop, unoptimized windows7 under everything- can't be good for efficiency or battery life.
it's just a preview.....
anyway, quote from ars
The core UI works, and it works well. It's fast and fluid, and it's very well thought-out. Multitasking, personalization, and interconnections between applications are all at your fingertips, and the Metro look-and-feel ties everything together.
The developer build being given out today is, however, very rough. Some demonstrated features, including speed bumps between groups and semantic zoom, aren't implemented in the build. In a few hours of usage, we've experienced regular application hangs and one total system hang. Microsoft isn't calling this a beta, and isn't claiming it to be anything other than a preview, and that's appropriatethis isn't ready to be used as a regular, day-to-day operating system yet.
But even in this early state, Windows 8 is unambiguously a first-class tablet operating system.