Pros
Opportunity to build products/services at massive scale, and impact entire IT industries. Work with some of the best engineers and leaders in the world. Ability to move between teams within the company to keep your skills fresh and continue doing something new. The newer buildings are quite nice. Overall, not many structural problems in the company that aren't present in any organization of this size.
Cons
Can be very stressful, especially around re:Invent (in AWS). Many small teams makes it a challenge to find the owner of a particular tool/service, and creates challenges to implement large cross-team projects. If you get a bad manager/director, your experience will also be bad; this is not the norm, but it happens. Employee perks are just OK.