Main feature changes is DB monitoring is available using DB agent(you will get SQL Query plan, bind value, etc..) and web dashboard concept enhanced in 6.3.
Currently Dynatrace7.0 going to release in May 2017.
Since the upgrade was from 5.6, the sum of all the release notes between 5.6 and 6.3 should be read.
I have a PDF detailing what is new and awesome from 5.6 to 6.2, which would go a long way to summarize the massive amount of differences.
If you want a copy, just email me. (dave dot mauney at dynatrace dot com)