Pros
The technology for their web sites is mostly up-to-date, although there were a couple applications that were old and very difficult to work on (for example the GameInformer site, and also the gateway home page on GameStop.com). Their culture is to keep up with the latest technology. They used Git source control. They don't overwork their programmers. Staff usually worked normal hours, except on release days when staff needed to come in very early (ie. 4-5 AM, but then they left early). If you like a very casual office with game-oriented themes all over the place, then you'll like the office. Dress code was jeans and sneakers. When I was there (2014-2015), management had a priority of more communication with employees. They were heavily into agile and scrum, which could be a pro or con, depending on your perspective. The computers provided to developers were powerful and speedy laptops with a SSD. On the business side, financial analyst types (outside the company) always seemed to be predicting the demise of GameStop, but GameStop seems to be able to find a way to survive and even prosper. So innovation and change is essential in this environment.
Cons
There is a lot of bureaucracy and administrative roadblocks. Getting a project approved, even a small project was a horribly complex administrative process (there was a name for the process but I can't remember it). While the approval process was taking forever, there were a bunch of contractors including me who had little or nothing to do. There is an excessive number of managers for the number of rank-and-file, and the managers just seemed to be helping IT departments get through the administrative process. There was a lot of turnover during the 9 months I was there. A couple highly-regarded tech people left, and one skilled programmer just left his badge on his desk one day and said he was not coming back (I don't know the story behind that departure). While the game-themed decoration in the office was nice, the IT area was in an added-on floor in the warehouse with no windows and not enough space. It was keep fairly dark because that's how most folks liked it (but I hated the dark, windowless cave.) Full time employees had their own cubicles but contractors generally shared small cubicles. In early 2015 they had the idea of jamming teams into small rooms to promote communication and teamwork, but that was totally unnecessary because our low-wall cubicles were adjacent and there was plenty of communication. One older woman in QA, who kept her cubicle nicely decorated, became terribly distraught when she was told she would be jammed into a small room with a bunch of developers. That whole situation was botched by management, in my opinion. (The move was delayed and had not occurred when my contract ended) Among management, there was a huge belief in the scrum process. From the developer perspective, there were short daily scrums, but also regular grooming, planning and review meetings. The managers were always working on the statistics, like maintaining "velocity", and there was probably some number-cooking. In my view, the administrative effort involved in the highly formalized scrum process vastly outweighed the productivity benefit. But if you want to work in a scrum shop, then this is a place to consider.