mjmd,
"Compatible" is probably not the best word to use as you go from one edition of SQL Server to the next. The idea is that as you pay more money, you get more features.
As for AC not giving out the SA password, that has more to do with keeping support costs down more than anything. Security isn't even on the table. The reason I say that is because if a bad guy can get on your machine with Administrator rights, that bad guy can just take a copy of your Amazing Charts database files and do with as he pleases. Regarding the redaction of medical records, that is the practice's problem, not Amazing Charts', as far as I can tell (I welcome further discussion on that).
JamesNT