Apply discount based on the method of payment. Possible?

The payment module has a condition for the customer's selected payment method, but the problem is that information won't be saved to the order and available for pricing rules until after the form is submitted. This means there likely won't be any notification to the customer that they're about to be charged more, so you'd have to figure out how to visualize that fee yourself.

Additionally, many payment services prevent you explicitly charging your customers fees for certain types of payment. I'd make sure you're covered legally before advertising this is what you're doing on the site.

@rszrama: you're right, but how could be possible to solve this issue?

Really it's up to you to either place a notification on the checkout page or find some other way to visualize the percentage. Your strategy depends on how you've built the site; there isn't a canned solution to do this.

@rszrama: next days I will try to add a custom line item with the fee (not % but a fixed value) but I need a way to reload the review panel with the new line (maybe with ajax?) or adding an extra panel with the review after choosing the payment.

From you experience what do you think about a function called via ajax when the payment is selected which add the new custom line value (on the order object) and after reloads the preview table?

Thanks again! :-)

That should be feasible; just make sure you also remove it if the customer goes back to another payment method. : )

You'll want to make sure the review pane is themed in such a way that the order total area is still visible, too. In a typical install I often won't see that b/c of the user account and billing / shipping address sections. It should be easy enough to condense those sections with an alternate theme template for the review pane.