Microsoft has posted the change log for Windows Phone 7.8 OS. The version number of the updated OS is 7.10.8858.136 but Microsoft calls it Windows Phone 7.8. The update will be rolled out to Nokia Lumia 900, 800, 710, 610, 510 smartphones.
Here is the change log:
Start. Provides re-sizable small, medium, and large Live Tiles so you can customize your Start experience in new ways.
Accent colors. Expands the number of available accent colors to 20.
Lock screen. Improves the lock screen experience with accidental wipe protection features and the Bing image of the day wallpaper.
Marketplace and Xbox. Expands Windows Phone Marketplace and Xbox support to new countries and regions.
Fonts. Enhances the Chinese font and improves the appearance of Arabic and other languages.
Other improvements. Includes many other improvements to Windows Phone.
Source: Microsoft