Microsoft have announced that the next version of Windows Phone 7, code-named "Mango", has officially reached RTM (Release To Manufacturers) status. This means that the final build is done and that handset manufacturers such as HTC, Samsung and now Nokia will be able to get hold of the OS and get it into their devices.
Mango has been available recently to Windows Phone developers through a programme on the MSDN Create website, but installing it on devices came with many warnings: the build would not be supported; it would void your warranty; you wouldn't be able to take backups, so all the data you created on the device would not be saved; and you would have to re-install the original OS from a backup before you could upgrade to the official Mango release.
The headline feature of the Mango release is the arrival of Internet Explorer 9 on mobile. This includes a vast range of HTML 5 technology support, and should be a great benefit to developers building for the mobile web. App multitasking has also arrived, reducing the amount of time users are waiting for apps to be restored from tombstone, and increasing the flexibility for app developers.