The beta releases of the Windows Phone Developer Tools that support Mango are now available for download. Developers can use this beta release to get ready for the upcoming Windows Phone OS release. The new application platform capabilities coming in Mango deliver the top features.
What's so late. Developers now have Mango (or at least a pre-release) but they can't submit any new apps till Mango launches, which will probably be Sep/Oct. Plenty of time to work on apps that take advantage of the new APIs.