The attrition is very high which is not good for the moral but again those people who are leaving now will call you some day with a job offer.
Agree with other reviews that you should know a lot of stuff before joining Amazon because there is no time to learn or take a class on anything. It is a sink-or-swim environment. Taking this into account, I would say that entering Amazon is probably better as the second job when you already know quite a few things, learned to code well, understand how to manage priorities, and now it's time to turn your brain on full throttle.
Amazon has the worst choice of medical plans across pretty much all high-tech non-startup companies in the area and I don't count MS at all here.
Honestly, I do not recommend Amazon to my friends because it is not a comfortable place to work at. There is a lot of pain going on here and I'm not enjoying it but for myself I consider it as the growing pain.