I know this thread is getting old now, but here's my opinion:
Millers/MPIX as my lab of choice.
Winkflash for bulk (read: 100+) of 4x6s since I can usually find $0.09 deals from time to time. They do not backprint Winkflash on them, just the filename.
WalMart for the gotta-have-it today print.
About WalMart: (And don't get me wrong, I am not a WalMart fan...) They have online service with several delivery choices: in-store 1 hour, deliver to store, and deliver to home. If you want WalMart, and you want Good Prints, choose the 1 hour in store. They told me that the techs there actually look at the stuff as it goes through and makes sure they're correct. This is NOT the case with the bulk unattended printing that is ship-to-store or ship-to-home. Their in-store lab is a Fuju Frontier printer, and the paper is Fuji Crystal Archive, Luster finish. That's a fine choice of paper for most applications, and when they are QCing it for me, I can't beat it.
Had gear, but sold it off. Starting back in with a SL1 / kit lens. Looking to expand the collection.