As with other software updates the roll out will be gradual, with some markets, and some devices, getting the update before others. In general unbranded devices will receive the update before operator locked devices. That's because operator approval is generally required before an update is made available.
Microsoft may also be choosing to stagger the update in order to perform a real world check, before proceeding with the full roll out. Microsoft has recently said that it expected the Windows Phone 7.8 update to be made available in early 2013. This may well remain the case for most devices.
The software update is delivered through the Zune Desktop client (Windows), or the Mac Connector for Windows Phone (OS X). Your phone will automatically alert you once the update is available, though you can also manually check for an update through the desktop software.
Image credit: WP7.nl
What's in Windows Phone 7.8?
We've yet to see the Windows Phone 7.8 update on any of our devices, but when we do we'll bring you a full run down of the update process and what's in the update. Our previous story on Windows Phone 7.8 details what you can expect.
The key new feature in Windows Phone 7.8 is the updated Start screen with support for re-sizable tiles (three sizes). Microsoft clearly see this as a critical feature saying that "the new Start screen is one of the easiest ways to make the phone reflect your style, your passions, and your personality".
In addition, the number of accent colours are doubled to twenty, the lock screen adds support for automatically using the Bing picture of the day as the background, and there's also lockscreen support for a PIN/password challenge to prevent accidental device wipes on phones connected to Exchange accounts.
In addition to the updates provided by Microsoft a number of Windows Phone manufacturers are expected to provide additional updates. Some of these will come in the form of software updates, and some will be provided through apps distributed in the Windows Phone Store. For example, Nokia has said it will be providing a number of new experiences including Ringtone Maker, Bluetooth File / Media Transfer, and additional camera extensions (Cinemagraph and Smart Shoot), similar to the way it earlier provided Contact Share and Play To after the Tango software update.