Nokia Lumia 900 owners on the AT&T network rejoice as the Windows Phone 7.8 update has been made available for download through the Zune PC client. Visual tweaks that include multiple Live Tile sizes, more theme colors, and an improved lock screen with the option for rotating Bing home page images are now made available through the Windows Phone 7.8 update.
More features in terms of the Windows Phone 7.8 update can be found here.
Source: Nokia Care US (Twitter)