I've never liked them,
They thrive on offering a few dollars for a trade in then resell it for $40 (assuming it's $45 new).
There's literally nothing there used that's ever a steal, I mean never. All of their used games are set at a marked rate, which means at any time you can go on ebay and find the exact game, at a buy it now price less than what they offer.
There's 2 other used games stores here in Houston that I genuinely like (although 90% of my used games are bought on Ebay or occasionally amazon). What I like about them is that used game prices aren't always set. The store I visit the most (there's 3 on my side of town) is GamesPlus. When they have too many copies of say Dragon Age on PS3, they'll mark one or 2 down to a very low price, like a quarter or more of the value it is new. I just bought all 3 Resistance games at $2 each used, I think that's a steal, they had them marked down because they had so many copies in stock. They'll also consider discounting if you talk to them right, like "hey I'm buying this used N64, can you give me 2 free games of my choice?" Etc. That's a business model that encourages customers, I still can't understand why I see people inside gamestop.
I can say this though, in early 2000s, they were still selling SNES carts in giant bins. I picked up Super Metroid, Mario World, Zelda link to the past, and a few other popular games for maybe $5-$10 each. Go on ebay now and see how much Super Metroid goes for.
Wondering how Gamestop is going to survive once all physical game discs stop being made, since a lot of their business is based on new releases, where as the 2 used games stores I visit rarely deal in new games.