John asked a very relevant question in a comment on the Revit 2015 Update Release 3 that prompted me to complete the rather overdue migration of the ADN Revit MEP sample add-in AdnRme to Revit MEP 2015.
I also took this opportunity to create a GitHub repository for it:
Much easier to share and collaborate on.
The enhanced documentation now explains all the basics and points to more detailed discussions on everything else there is to know about it:
Revit MEP Sample Application for Revit MEP HVAC and electrical – Demonstrate use of the Revit API for MEP specific tasks.
Use of the generic Revit API for HVAC specific tasks, using only standard Revit element properties and parameters:
Use of the MEP specific API to traverse an electrical system and display its hierarchy in a tree view.