Windows 10 Mobile build 10166 rolls out to insider preview users to those on the fast ring, According Gabe Aul “There are lots of small changes and features tweaks and big improvements to the user experience in this build”. Gabe Aul the head of Windows insider program also told that “but our major focus over the past few builds on mobile has been about improvements to core quality.”
Most of the known issues we listed for Build 10149 have been fixed. We also fixed the issue where the post-upgrade migration status screen was missing, which made the Lock screen appear frozen without the date and time for up to 10 minutes. The post-upgrade migration status screen should appear normally now. We also fixed the issue where you were unable to unlock your phone after entering your PIN and it keeps letting you type even though you entered your pin correctly that was caused by a TPM issue. The colors in apps should now appear correctly including in including the titlebar in the Outlook Mail app which is no longer orange. And we also improved reliability of app downloads and updates from the Store (which is now no longer marked as “Beta” and the old Store has been removed).