Adding and subtracting "credit" from a user's account
Are there any contrib Commerce modules to help set up a situation where some purchased products give the customer a "credit", while other products draw from that credit? (I can't find any, but maybe I'm being too literal in my search).
If not, anyone have experience implementing something like this?
That's what [Commerce Userpoints](http://drupal.org/project/commerce_userpoints) wants to be. Last I tried (quite a while ago) it worked fine but I needed a couple of patches from the queue.