Pros
Opportunity to work on interesting, cutting-edge projects. Generally highly competent, intelligent colleagues. Good 'name' for your resume to leverage for another position.
Kontras
One of Bezos' fundamental values is 'frugality' and boy do they ever mean it at Amazon! Double-sided print jobs (for those awful memos you have to prepare and discuss in excruciating detail before doing anything) and stays in unsafe, sketchy hotels during business travel will be your life. No free phones here (although you may get a free IMDB Pro account, which is unintentional comedy at its finest). This emphasis on frugality is not shocking given the company barely breaks even but Jeff and his 'S' team doesn't pay the price - rank and file employees do. In an environment in which competition for talent - especially tech talent - has never been higher you would think they would at least pretend to care about their employees. Not so. When Microsoft looks great by comparison on this basis, then you know you have some work to do. They even went after a former colleague of mine, suing him for leaving for Google, even though he moved to California and they don't enforce non-competes there, which Amazon knows. They did this just to screw with him and to send a message to current employees who may be thinking of leaving (which is everyone below Level 8, at least). Cutthroat and awful place to be. Life is short - why spend it at a place that despises you? When my options vest shortly, I am gone.