As a registered Windows Phone developer, you have been invited to participate in Windows Phone ‘Mango’ Beta 2 for WP Dev Devices Program on Microsoft Connect.
This program makes a pre-release build of Windows Phone ‘Mango’ available to our developers, allowing you to test your applications on ‘Mango’ and prepare it for the upcoming update. Together with the recently released Windows Phone SDK Beta 2, this pre-release OS build allows you to test your code on a personal, retail device.
Once you accept the invitation by clicking through the link below, you will be asked to complete a mandatory survey, which provides this pre-release program’s required terms and conditions (guidance, voiding of your phone’s warranty, country limitations, etc.) that you must accept prior to having access to the update tool.
Looks like it voids the phone's warranty, but a twitter post from MS suggested they would provide support for one Mango beta device. Might have to give it a go...
Anyone else here got a developer unlocked device and going to get the Mango beta?