I helped a customer upgrade from 2013/7.2 to 2015/7.3. Overall went smoothly. They were previously having issues with duplications in CRM because in the past they made backup companies and didn't uncheck the CRM module, and that has completely gone away. We did notice issues with the Compatibility mode needing to be off for CRM in IE, but on in Sage 100 for the dashboard to display graphs. But that apparently is fixed in PU3. So when you upgrade go to PU3.