I never used one of these, partly because it seemed like it would create significant friction if I needed to return the item. What is the return/refund process

I never used one of these, partly because it seemed like it would create significant friction if I needed to return the item. What is the return/refund process like with these services? I assume they get the refund from the merchant and then disburse your part of it to you? Does it go smoothly, or do you have to chase things down?