Lemme list out the changes I've noticed so far:
-fingerprint scanner works much faster and now uses marshmallow fingerprint APIs so you can now use fingerprints for apps that support it.
-HiFi DAC works with more music players, as well as YouTube.
-No more YouTube issues: animations are now smooth and 1440p playback is flawless.
-second screen is the new place for the tools bar with Capture+.
-phone feels a bit smoother and gaming performance is better now.
-battery life has improved quite a bit. Highly depends on if you have apps set for Doze to ignore.
-notification panel now splits notification volume and ringer volume. Hated it at first but like it better now
-smart settings works well now. Too well I might add. Location detection is still sometimes glitchy but location based settings register reliably compared to Lollipop.
-second screen when the phone is off is brighter now and controls are more fluid. As a bonus, music controls are available even when no music app is open.
-popup notifications now register inn the second screen more. Hangouts and Skype still show a heads up on the main display but in the case of Skype, relegates to the second screen with extra messages like a chat for example.
Posted on an LG V10