Following today's earlier tweet, Microsoft had indeed something good in the pipeline, as long as you are a registered Windows Phone developer. Starting today, developers can upgrade their Windows Phone 7 smartphones to Windows Phone 7.1 build 7661 - formerly known as Mango! Registered Windows Phone Marketplace developers will receive an invitation from Microsoft Connect that will provide access to a firmware update for retail Windows Phone device; yes there are no special developer devices involved anymore. To get the Windows Phone 7.1 Beta bits, you must have an active, validated App Hub account and you may update only one phone per developer.
As with all Windows Phone updates, the Mango Beta updates also involves Zune that redirects the phone update requests to a special server. Otherwise, the update process is fairly the same as with regular Windows Phone 7 updates where the phone is connected to the PC, Zune recognizes that an update is available, downloads it and flashes it to the device - that's it.
The update is now available to developers in Australia, Austria, Belgium, Brazil, Canada, Denmark, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg, Mexico, Netherlands, New Zealand, Norway, Portugal, Spain, Sweden, Switzerland, United Kingdom and United States.
It's not yet ready for end users but will be available to all Windows Phone 7 users later this fall.
Cheers ~ Arne