Pros
There are very few places that operate at this scale. The problems that need to be resolved as a result of this are usually interesting and never ending. Do well with regard to performance metrics and with a good manager, there is decent growth potential. Boredom won't be an issue with all the activity going on. Two or three day weekends are an amazing thing. Work does not follow you home when you go off shift unless you want it to. If you are able to succeed under an Amazon work load, you can excel anywhere.
Cons
Your experience is dependent upon the competence of your local management chain. I saw multiple talented employees not getting the opportunities they had earned due to mismanagement immediately above them. Switching to a team under different management was able to resolve these issues, but this was not an easy process when I left. Employee training process is inspired by "Lord of the Flies". Work life balance is weak if you care about your career. If you have kids, this is not an ideal situation to place yourself in unless you only have partial custody. You won't get a full Saturday and Sunday off unless you use leave of some sort. 10-12 hour shifts are the norm. Overtime is mandatory for some teams, which likely will not be explained during an interview. Most career growth paths require a move outside the Northern VA area. Like most tech companies, if you come in with low pay, it will put a ceiling on your pay raises for the duration of your career. Play hardball when negotiating, especially if you are converting from a contractor to full time, as the company already knows what your potential is. HR is a train wreck.