In the Microsoft changelog it points to improvements where reliability, performance and stability are concerned. Not only that, it will also include a fix for a problem that could result in unexpected battery drain while the phone screen is off. There are also improvements made to the update system in order to prevent phones from entering a state where attempting to take an update may lead to errors 0x800f081f or 0x80070570.
Other fixes include doing away with an issue that caused select phones to finish the initial setup wizard with an incomplete set of app tiles on the Start screen, while reliability of USB-C connections have also been improved with Cortana getting a bump herself as well, where music playback would not resume after dismissing an incoming text, and a problem with Quiet Hours not setting automatic rules for every day. Well, if you are a Windows 10 Mobile user, what are you waiting for?