"Great news for those waiting for WP7.8 update for their Lumia 510, 610, 710, 800 and 900. The Firmware build 8858 appears now at NaviFirm for all the above devices and it is available for most of the European countries and APAC variants. So, pretty strong indication of near future roll out of the update for most of the devices."
If you are adventurous, you can download the update via NaviFirm, but we strongly recommend holding out until Nokia rolls out the update officially.
Windows Phone 7.8 is Microsoft's olive branch to existing Lumia users, having announced that they will not be eligible to receive the feature-rich Window Phone 8 update.
Microsoft finally shared some Windows Phone 7.8 details recently. The update will add new features like a new start screen UI with resizable live tiles, as found in Windows Phone 8. The update brings Windows Phone 8 branding to existing Lumia devices on the splash screen and icons for Games, Office and Windows Phone Store.
Windows Phone 7.8 doubles the number of theme and accent colours to 20 and adds other new lock screen features: the option to automatically display the Bing Picture of the Day plus the 'A1B2C3' PIN/password challenge to prevent accidental device wipes on phones connected to Exchange accounts.