Pros
You will be working on projects that support or challenge other industry giants. Most of the people I meet are interesting, intelligent and kind. There are many development opportunities for improving service offerings, infrastructure and tooling in an organization as diverse as this one. There is so much to learn here. Internal tech talks are frequent and informative. Most managers I have observed have been clear about expectations. Mine have appeared to be honorable, concerned for my development as an engineer and my well being as a human. Recent (early 2017) efforts to help identify and remedy work/life balance issues are relevant and effective.
Cons
Amazon is an orchestrated chaos with deep internal culture. It is not that this is bad or insurmountable but for most it requires about nine months to become acclimatized. As in many places employees must be aware of their need for life balance and can easily burn out. The Seattle housing market is not sane. Childcare costs are staggering.