Jack,
We also are not Medicare/Medicaid, and MU means nothing to us also. We have been using Medware since long before we started AC. Because its use is so ingrained, I doubt we will switch even if AC comes out with its version. Medware is totally stable, I won't get caught in any "Post beta testing" nightmare, and as mentioned above, it puts a human in the loop between what button I push in AC and how a claim actually has to be coded for payment. We have a skilled coder who knows a lot more than I do about those issues. Additionally, a real PM system has a bunch of reporting functions built in that allow you to compare income from various sources and time periods, which helps in making practice decisions. Yes, I know it can be done in Excel, but it seems easier to use a pre-formatted report.
I also would strongly encourage the view that you will be much happier in the long run to get a standalone system like Medware in place and then consider switching to the AC system a couple of years from now if it still seems important.