AT&T and Microsoft tonight have begun pushing out Windows Phone 7.5 build 8773 aka Tango to the Samsung Focus 2 (see our review). The previous version of the OS was version 8112 aka the LTE build. First reported in our comments by MDiBo, we were able to verify on our own Focus 2 that the update is indeed live...

Windows Phone Tango brings numerous small fixes to the OS, including multiple images in MMS, send ringtones (MMS), more reliable push notifications, new wallpapers and other optimizations.

After the OS is updated users will be prompted to do yet another update, which will install new Samsung firmware to coincide with the OS upgrade.Though we have not verified what this firmware update contains, it usually fixes minor issues related to the camera, proximity sensors, volume controls and potentially the display. We’ll try to verify any changes over the next few days.

We did test other AT&T Windows Phones including the HTC Titan, Titan II and Focus S and were not able to verify any OS or firmware updates for those devices at this time.

Update: The Tango Update for the Samsung Focus 2 took about thirty minutes.  Times will vary depending on how long the backup stage takes.  When all is said and done the new Firmware version is 2103.12.10.1 and a new Radio software version is 2103.12.9.1.