This build is interesting for two reasons; firstly it contains an important bug fix for an issue Microsoft introduced in build 16288 which caused a boot issue on Surface Pro 3 devices; and second, this is the first build where there are absolutely NO feature improvements or additions mentioned, it is a purely bug fix build.

As such, the change log isn't very long, Microsoft have fixed, in their own words:

• This build has the fix for the bug that was causing some Surface Pro 3 devices to end up in a “unbootable” state where the Windows OS will not load and it appears to be stuck on a “spinning dots” screen. After installing this build, Surface Pro 3 devices should no longer get into this state. If you have a Surface Pro 3 in a bad state – follow the instructions on this forum post to get back up and running.
• We fixed an issue on Dutch builds where explorer could go into a crash loop if an app-requested downloads notification popped up from OneDrive.
• We fixed an issue where expand.exe couldn’t expand CABs that contained Japanese characters in the file name.
• We fixed a race condition that could result in window content being transparent (but showing the window frame) or stale after unlocking your desktop.
• We fixed an issue resulting in some Insiders seeing error 0x800B010C when attempting to upgrade to the last few flights.

The full release notes and announcement are here