Android police have generated a change-log with all details. Here what's new.
Android Police "Not much has changed. Sadly, the list of commits is limited to fixing a handful of relatively trivial and uncommon bugs.
Even though the differences between r3 and r5 are minor, remember that the devices receiving this update are only just now taking the step up to Android 5.1. That means they will also enjoy all of the perks that came out with the release of 5.1, and the improvements made in 5.1.0_r3."
Here is the Full change log: Android Police