Pros
In general, the quality of people you work with is much higher than that of other phone shops. Amex seems to care about their employees, they make a concerted effort to provide decent benefits and room for growth. They have a gym onsite, a nurse onsite, multiple game rooms stocked with consoles, ping pong tables, etc. It was a lot of fun to work here.
Kontras
Ultimately it will be the low wages that can divert you away from a future with the company. Unless you are lucky enough to get into a professional role and in upper management's pocket, the growth (while abundant) is slow and difficult. Given the size of the company, the competition for one-off roles is very stiff. I suppose that's good as there are many bright people working here, just too slow for my ambitions.