Windows Phone SDK 7.1 RC is now available. You can use this version of the tools to create Windows Phone Mango apps and submit them to the marketplace.
You need to uninstall previous versions of the tools before installing this version.
These tools enable you to create Mango-targeted applications that include all the new Mango features. In addition you get some new tools such as the isolated storage explorer for viewing and debugging files in isolated storage, the memory profiler, an addition to the performance analysis suite, and the Marketplace Test Kit, which enables you to assess the marketplace readiness of your application before you submit it to the marketplace. There is also a great new emulator screen-shot tool that makes it easy to complete those final steps for marketplace submission.
The tools are here, and the marketplace is open....now is the time to get on board with Mango.