Since this thread is about rating our LDS's, and BlueDolphin has brought up a "large chain sporting goods store" In Southen California, I'm quite sure I know this store: Sports Chalet. This is a well known chain store to most divers in this area.
I'll give you my impression to illustrate what I see as the pros and cons of a large chain store.
Modern, clean, well lit, spacious, good displays, good product selection (at least for major brand items and accessories), good stock at hand, overall an attractive place to shop.
Multiple locations advantages, if something is not in stock, you may be able to find it at another branch, and go pick it up if your willing to drive a few miles; Plus all the other advantages chain stores offer.
Their prices are competetive or better than most local dive shops, specially compared to the smaller shops. They get beat by the "low price" online shops, although some of their sales can make the difference negligible or even be a better price than online.
They offer most of the standard services: rentals, air fills (no nitrox or other mixes), classes, repairs. They are not as accomodating on gear tryouts as some other shops, but like any big chain store, if your demands are reasonable and you speak to the right person, you can return or exchange just about anything.
Now its time to mention the X factor - employees and the services they provide. Keep in mind there is relatively high turnover consisting of some full time and part time labor.
The service is overall friendly and helpful, unless you walk in when some of them are watching a sports event on tv. The information and advise you get is a toss up. You may get a knowledgeable diver who knows what he is talking about and give you very good advise, or you may get the newest youngster who just got his certification and knows what a reg is and what a bc is. Did you see the period? Then again you just may get the good ole charlatan who has no right pretending to know something he knows nothing about. "If you push this button the engine starts and with this one the wings open up. Now, which color do you want?" I could'nt help it, I made the quote up, but not the part of which color do you like. I've also gotten when asking about products - they all do the same, which one you like?
When it comes to classes, do your homework about the instructor. They are a 5 star padi shop. So they passed the requirements, don't assume all instructors are good.
Same thing for repairs, they have a central location for repairs and I have heard of mixed results. In something as simple as an air fill I've have been helped by a new sales person who did'nt know what the 2400 psi with + rating meant. I explained it, but sure enough when I went to pick it up I had 2400.
Bottom line, there is no consistency in quality when it comes to service. You have to search for a good knowledgeable sales person or instructor, and they do have them. There is going to be variance in quality of service in any business, it is just more pronounced in the larger ones, specially when employee retention is not a priority.