In this release we've removed the old AppCache offline support, since all major browsers now support Service Workers and AppCache is on the deprecation path. Additionally AppCache could sometimes cause headaches with getting updates to work correctly, or could conflict with the alternate Service Worker offline support. Offline support will keep working (using the newer Service Worker approach); we've only removed the older technology that browser makers now want to remove.
Other than that we have a few fixes and updates, notably to ensure audio plays in Windows Store apps with the latest Windows 10 update. If you have published Windows 10 store apps, you should re-publish them with this version to ensure audio playback works as intended.