I asked one of the ACAD boys here and they only use the EPDM addin in Inventor, not ACAD. He said the main reason is because ACAD won't let you make the file writable after you have opened it read-only. So in that respect, there isn't much value in the addin. Now that being said, we don't use the workflow so there may be other functionality there that we don't use.
He also offered the opinion that if the DLL file is a .net file, there is only one version - your .net framework version on your machine compiles to suit at the time of usage.