The problem with GC is their training is just bad. The information within the company as far as promotions is all there, the problem is the communication is poorly delivered, and a lot of store managers and quite frankly inept, hire bad people, their friends, and are kept in place by bad DMs.
However, if you get a store which knows what they are SUPPOSED to do (i.e. honor the highest trade price guarantee, its a company policy if you find a competitive TIV which is higher GC will match and beat it by 5%), if they actually merchandise and price effectively (update the daily price changes, for the love of god they are on the printer daily), and actually tell the customer about current promotions, you can find rather good stores. The company does price match too.
I actively tell any customer coming into my store not only about current promotions but upcoming promotions, and honestly if your GC in your area sucks, please call the customer support number 1-8SPEAK-TO-US. It does get back to DMs, RMs and people will be replaced. In my own district I've seen a large turnover and quite frankly it's for the better.
Unfortunately the company is very subject to cronyism from what I've seen, but on the same token I've seen some very good managers who actively try to make the store a viable alternative to GS. I started shopping there because the GS in my area were terrible, the employees just sat around bitching about how terrible their jobs were so I worked for GC because the manager there was a good guy. I still shop my competitors and my store does in fact have great prices on used games, great prices on new games and accessories, used systems are about the same (except DS lites are the only one cheaper that I've found).
Just my own experience with the company when I started as a lowly grunt my store sucked, it was a mess, improperly priced, no one knew the promotions or enforced them. A year later, everyone coming through my door knows what they can get deals on, gets the right discounts, and if its not in my store, I will get it from another one. If you go into a GC and ask for a game that they don't end up having in stock and they won't check the onhands to see where the closest store has it, call that number. The tools exist in the company for it to be a good shopping experience, so call them out on it.