Pros
It's an easy place to earn basic wage without having too much invested or asked of you. The schedule is flexible, provided you don't need full time employment. If you want to work at the Gap for the rest of your life, management opportunities are available, but you really need to take on a "company man" attitude to get there. That means putting your own desires on hold and working for company first and your own edification last, but if you love the clothes, the retail environment, and the ups and downs of pop culture, you could certainly do a lot worse.
Cons
As with any big company, it's all about the bottom line, which doesn't leave a whole lot of room for the individual. On the plus side, the constant state of "reduce store operational hours!" means you can effectively have off any time you want -- unpaid, of course. Benefits are extended only to full-time employees, but stores run on such minimal hours that only one to three non-management employees will be full-timers. For the real-world, non-yes-men who make up most of the employee base, it's just a job, and there's no real motivation other than empty jingoism to do more than watch the clock.