What Windows Phone 7 demo/reference applications have you seen which really made you interested in developing for the platform?
I know of Scott Gu's Twitter example and Foursquare. Also see here for MIX10 demo apps.
Other than developing games and re-creating functionality already present on other mobile platforms (iPhone, BlackBerry, Android), is there any good reference material and business benefits of developing for Windows Phone 7? Does the Silverlight dev environment really offer an advantage over what is already out there? My gut feeling is that this is definitely the case, but it will take some time for the platform to establish itself, if it does.