Pros
Strong culture of ownership - engineers support the software they create through an oncall rotation process. Note that different teams in Amazon - like any big company - operate differently, and some are much more mature than others. This means that even if you are more comfortable with structured processes, there are several places where you can feel at home and contribute meaningfully. Plus -- its a VERY high-energy place.
Cons
Strong focus on customers, sometimes at the cost of employees. Benefits package could be better, and work-life balance is really up to you. Mostly, since we are a 24x7 internet retail site, be prepared to be up some nights and weekends firefighting technical issues, dealing with clients or addressing management's questions on product performance.