Up to now, I wondered how the metro UI would fit for large screens and thought that it wouldn't work. But after seeing a video of it in action, I like it. I especially love the fact that you can drop down into the traditional way of doing things and run some non-metro apps. I do a lot of work inside powershell and can't imagine Windows without it anymore. Still have one machine that has to run Windows XP, and that too now has powershell.
Think the charms are great too. Hope there will be pen support, and good support at that because the only way I envision working with a slate/tablet is that it have a stylus so I can take notes. Or just show off.
Downloading the preview bits now. And that's a big deal. I never run beta tools (let alone pre-beta) for anything with the exception of Orcas, and VS2010 which I just couldn't wait for. This here will be interesting.