i worked part time at one for a few years to make some new friends, earn a bit of extra cash and save a bit of money on games. i enjoyed the job and didn't mind selling pre-orders or subs or whatever. i could tell when someone didn't want to hear it, and our manager never really slammed us for having bad numbers so long as we were telling people about them.
generally we'd have one person on the staff who would push that stuff on everyone and everything, who didn't understand that good numbers and good customer service weren't the same thing, but overall the staff there were friendly, knowledgeable and good to work with.
then some of those staff were forced to split open new product and take out an advertised free copy of Deus Ex: Human Revolution from the PC version. i knew that Gamestop would end up apologising to the fullest over that crap, but i was expected to tow the company line on something that i knew was wrong. i handed in my notice and walked away.
whatever my price is, it's a lot higher than i was earning working 8 or so hours a week at Gamestop.
so really, it's the same as any retail job. if the staff there are good, it will generally be a good experience until corporate expect you to do something that fucks over your customers and have you on the frontline defending it.
i still shop there. still get on with everyone. i think my old manager would take me back in a heartbeat and i do miss it... but i'm not selling myself out on those principles.