The update was first reported by Chinese blog ITHome, which says the new build contains improvements and fixes for a number of bugs that users encountered with the initial build. Such improvements include new settings for the vibration switch button, improved battery performance, and better camera performance when taking pictures at close range. Users should notice fixes for screen freezing and alarm clock issues, along with syncing problems with Outlook Mail as well.
We should note that we haven't yet seen the update hit our Mi 4, but it should be rolling out now. Let us know in the comments below if you've had any luck with Windows 10 Mobile on the Xiaomi Mi 4, and also be sure to check out our hands-on with Microsoft's Mobile OS running on the handset.