Too bad it didn't arive sooner, I had to make a small app using some mobile technology this year at the faculty and I had to settle on Windows 6 SDK, wich was well what you would have expected from something written in 2007.
It looks pretty nice, but that's to be expected since it will try to expand on the market that smartphones like iPhone is gaining more and more terrain. Microsoft is trying to keep it's products in line with the design that operating systems like Vista or Windows 7.
It's my feeling that this only the beggining of the other releases they have scheduled for this year (or the next), releases like: Windows 7, Visual Studio 2010, Office 2010, .NET 4.0. They might be comming with other things also, but I those I named are the ones I'm interested in, office not so much, but who knows what my work will lead me to.