11:45 AM
As the title says, there's a problem with this build that will require you to go back to Windows Phone 8.1 in order to upgrade to this build.
According to Microsoft's Gabriel Aul, the company's engineers have discovered a bug yesterday that caused phones upgrading from build 10536 to get stuck at a blank screen after this new build is installed.
It looks like Microsoft preferred to release the update nonetheless rather than making Windows Phone fans wait a little bit longer for the bug to be fixed. So, the new build has been released as a single update from Windows Phone 8.1.
You will have to go back to Windows Phone 8.1 to upgrade to this build
If you want to upgrade to Windows 10 Mobile build 10549, you will first have to go back to Windows Phone 8.1 using the Windows Device Recovery Tool.
Then, you should install the Windows Insider application, choose the Fast ring, and reboot your smartphone. After that, the new Windows 10 Mobile build 10549 should download and install on your device.
But if you think the process of getting to Windows 10 Mobile build 10549 is too complicated and not worth your time, then you can remain on build 10536 since Microsoft is working to ensure that you will be able to receive the next one.
However, those who decide to upgrade to build 10549 should be pleased to know that they will help Microsoft “test the upgrade path that millions of Windows Phone 8.1 customers will take to upgrade to Windows 10 Mobile,” and receive the company's appreciation at the same time.
The new build brings improvements to Cortana, messaging app improvements and diverse emoji. Lots of fixes have been provided in this build as well, and Lumia 1020 users will be pleased to know that Lumia Camera app will no longer by uninstalled.
