I miss not getting to go to Mix this year, but I've started watching some of the video, starting with the day 1 keynote. (For some reason there's some kid with a yo-yo, then some video, before you get to the actual thing.) When you get into some of the app demos (the eBay one is dull), it's pretty exciting to see the potential of the new Windows Phone, especially from a developer perspective. I love that I can take something like CoasterBuzz Feed and easily put it on the phone. I'm even more excited with any mobile dev platform that doesn't require an awful language like Objective-C and underbaked tools like X-Code and the interface builder.
Will I switch to that phone? Probably not in the first year, as I've got some time left in my iPhone/AT&T contract. The difficult thing for me is more the music integration. I'm not tied to iTunes DRM (all of my music is now DRM-free), but that ecosystem that includes iPods and the AppleTV make it a little harder to simply bounce off of it. I think in that interim time, there's a good chance that some enterprising developer will figure out how to do sync with an iTunes library, in which case I'd probably be all-in, provided the hardware OEM's come up with a solid design with great battery life. I love the idea of being able to develop apps for it with the skills I already have.