Pros
Amazing discount, you get to buy stuff at cost. I got pretty lucky and my coworkers were awesome. You learn a lot about gear and talk about music all day. It really is a great place for networking, if you're friendly with the right customers you can use it to further your own career as a musician.
Cons
The company does not care for its employees and the turnover rate is unbelievably high. We lost a lot of valuable talent in the year I was working there and no efforts were made to keep these employees whatsoever. It is also pretty much a self-taught job, the "training" modules will do you no good on the sales floor, so if you are just starting out, be prepared to be lost a lot and fumble all over yourself until you get your bearings. And when they hire new people, get ready to be the one training them, which frankly takes away from time that you could be making sales. Also, their computer systems are unbelievably slow and buggy, to both employees' and customers' frustration. Considering that they haven't updated their in-store system since the 80s (c'mon it's in DOS guys), that's to be expected. And don't fool yourself, it is still a retail job at the end of it all, and you will be working nights and weekends if you leave your availability open for that. This means that you won't be able to do gigs on weekends if you close all the time, unless you constantly move around your schedule. It is very unstable in this way, so if you're looking for some sort of day job in which you can work by day and gig by night, this isn't it. Ironic right?