About two years ago, I processed several C41 rolls through Wal-Mart. It was impressivly cheap, and the prints appear optically printed.
I was pleasantly surprised. These prints are actually pretty good for proofs.
I quit using them though when I saw my negatives coming back with a staple in the end of each roll. It caused marring of whatever negative happened to be next to it in the sleeve. I haven't used them since.
Still, it is head and shoulders better for proof prints than anything I have locally.