When making my usual OV purchase, my local cashier told me that "everyone else buys the flat cards." I asked her what she meant and she walked over to the gift card rack and grabbed two VRs.
Register was hard-coded (as expected). I'm not sure if she just didn't realize you can't use a credit card. Cashiers at this store saw Frequent Miler's piece on Yahoo. They are now very interested in and supportive of what I am doing. They used to just run my transactions with apathy.