Hide Checkout Steps can remove the Payment Method step (by hiding it and proceeding through it in the background). It doesn't hide the Billing Address step since customers generally need to be able to change their billing address, but if you want to hide that as well I can give you some code for Hide Checkout Steps that does that. That would hide both those steps, and proceed to Confirm.
Keep in mind it just *hides* the steps, so it still has to process them in the background. This adds a slight delay while those are processed, but it's not too significant.
Again, please try out the demo so you can understand how the extension works, and if you decide to purchase it, contact me at
www.getclearthinking.com/contact if you'd like the edit to hide the Billing Address step as well.