Yesterday, we released a refresh of the Windows Phone SDK 7.1 to our registered developers. The refresh carries two parts: we released an updated release of the Windows Phone SDK 7.1 (LKG-26) and the Mango OS (Build 7712).
With WPSDK RC about a month away, now is the time to update your app to Mango:
Then the phone,
The process to update your phone with build 7712 is pretty straight-forward: this build is not a RTM build – it’s still a pre-release build
For additional details, refer to the Windows Phone Developer blog.