The AP payment I did today was via a Visa $200 card I bought and added to AP yesterday after I registered it. I have not added a MC to AP to know of it works. I believe it does as somewhere in this long thread is someone who said both work with AP. The previous rebate deal was only MCs so they should have first hand knowledge.
When you added and used on AP, did you just put your name(name of AP account) and address of AP account? I ask since GCs dont have name and address on them.