I am using MedFX, the company that from which AC bought the PM program. I have not upgraded to AC because they are currently swamped and I am letting things settle down a bit. The two are almost the same. I understand AC has a few tweaks to make it a bit more user friendly. AC version is $50/ month less expensive and they use a different clearinghouse.
Overall, it is a very powerful program with lots of options and choices but it is not very user friendly. For me and my staff it works.
It took several months to get up and running, I understand that is also the case with AC although they are working to streamline the process somewhat.