For what it's worth...
Over the years we switched software billing services three times (none involving AC). Each time we were promised the patient and billing data could be cleanly transferred. Each time, the data was totally corrupt. By the third time, we knew what was coming, and did what we did the previous times right off the bat; make all patients re-register and re-enter their data, run new charges on the new system, and keep the old one alive until the AR were thoroughly run out. It also served to clean up a LOT of bad phones, addresses, insurance data, etc.
David Grauman MD
Department of Medicine
Commonwealth Health Center
Saipan, Northern Mariana Islands