I think it's terrible. I don't think there's much that needs to be said, especially in an environment where the merchant has no choice. The problem here is that the customer sees the advertising: if you use this product you'll get five points instead of one, or you'll get points, but if you use this other product you won't. You create the demand at the consumer level, because it's not costing them more, and you're making the middle guy pay.
You have products residing on the same card, and the mechanism they say you have to put on your cash or on your counter to accept that card is controlled by someone else. So you cannot ensure that the transaction is going through the cheapest route--