Pros
Making designs and customer experiences that go live and are used by millions of people is an accomplishment that I'm so proud of as a designer. Amazon offers that kind of opportunity. There is also exposure to incredible minds and personalities, and talent that inspires you to raise your game. I met, worked with, learned from, and became lifelong friends with amazing people here. Collaboration opportunities abounded, and ideas for continuous improvement were encouraged, and implemented with supportive data (which you got to research, write/mock up and pitch). What they say about project ownership is true, but you're as responsible for tooting your own horn and creating visibility around your project too. Type-A drivers probably find it easiest to survive here. In addition to working on meaningful customer experience design projects, I got a great business education. Designers have access to data and as much business and technical specs as they can stomach. There were fun prototyping explorations, and plenty of exposure to customers via a robust and supported usability department.
Kontras
Expect to gain weight, go on anti-anxiety meds, and resume your smoking habit working here because you'll kiss your life outside of work goodbye. You can never "coast" or just do your job--taking a "rest" by working less than 50 hours/week is a sign of weakness and losing your edge--eventually you'll be penalized for it. "Sustainers" need not apply, Amazon is only for aspiring leaders who launch stuff and then move on to the next sexy project. If you're even momentarily not interested in leading a team, or continuously working for a promotion, you're given a low performance review. I saw this happen to countless great people. Everyone does the job of at least one and a half, if not two, people, and continuing education is your responsibility and expense (in time outside of work), not the company's. Would also concur that it's essential to find the right team to work for--if you interview, be sure to read between the lines to ascertain how happy those on your loop are.