I'm lucky to live near one of those Amazon locker stores and the process has been pretty good. Just show up with the item, print out your return label at the koisk, put it into one of their bags, and drop it in the slot. Very little hassle.

That's a pretty weak advantage. My closest walmart is much further than my local ups/usps/amazon drop off. Also, don't forget that Amazon grew 30-40% last quarter y/y.