Pros
Amazon is a pretty good company to work for. Management takes product ownership very seriously. I work with some great people, and that's a big plus for me. The culture in Sunnyvale is more relaxed than the culture in Seattle and most of the horror stories you hear about Amazon are related to hourly employees at fulfillment centers, not engineering. (That doesn't make them less valid, it just means that I don't personally experience that.)
Cons
As with any job, your manager can make or break your experience. I started with a great manager. Great technical skills and great people skills. He left the company and now I'm stuck with someone who's technical skills are a bit out of date and his people skills are non-existent. My work-life balance was really good with my first manager; he strongly supported a balance and taking time for yourself and training. My new manager would rather have us at the office from 8 a.m. to 10 p.m., so individuals have to push back to defend their work-life balance.