Ian,
I haven't messed with this contribution yet, so maybe it already does this, but.... I was thinking it would be really nice if this contribution worked a little differently. Instead of charging MORE based on payment type, it should charge LESS based on payment type. This is just simple psychology - customers want to feel like they're getting a deal - so if I give them a 10% discount for paying with cashiers check / money order instead of a credit card, they feel like they're saving money - in reality I'm charging a 10% fee to everyone who uses a credit card.
Maybe this contrib already does this, but if not it would be neat.
Thanks!
Paul