REI usually has one or more service techs who have mechanics certification FWIW. I have seen guys studying the exam at REI too. Also, they really stand by their products and service. Very fair prices too for the service and fast. They remove freewheels for me without charge. They really are not a discounter, but a specialty retailer.
Bikes at the big discounters are assembled generally by 3rd party contractors who get a piece rate and are the same guys who assemble the gas propane grills. They work for anyone and speed is everything. I've seen those jobs advertised on craigslist in NNJ. Only qualifications; tools and a drivers license.
As far as bike quality, there of course is overlap of brands and models among the discounters and even REI with respect to Diamondback.
Here's a recent post on a Kmart bike.
http://www.bikeforums.net/showthread...from-Lands-End
LBS are hit or miss as well. Often peak season help in a busy shop are teens with very little experience.