I personally only use Mpix for anything unless I need it in an hour or so, then I will bring it into CVS and get a quick print. My 2 cents on
Walmart is that I will NEVER take or upload a photo to them again. Speaking of my local WalMart only, they took it upon themselves to like one of my photos so much that they used it to make calendars to use as advertising for their calendar prints in the store. They never asked or cared if it was right to do or not. It wasn't until I cornered the manager of the store and mentioned copyright infringement that something was done about it. They took the prints and shredded them (I demanded that I see the shredding done). So again, this was just at my local WalMart, but still, I would be weary of them in general.