Avantages
Some of the people I've had the pleasure of working with have been nice and very bright. It's really been a pleasure to work with them. Having a world class internet retailer on your resume if you are interested in the industry helps to get you noticed. Amazon has been incredibly successful (we even had a good Q4 despite the economic issues plaguing other companies) so if you do work here you can learn how it happened. You can also see first hand how what works when your small can create a lot of internal turmoil when you get big if it doesn't change.
Inconvénients
Launching products is considered more important than ensuring that code is robust and documenting how things work. Despite Amazon's large size it doesn't have a lot of well developed work processes & groups often have different goals & missions. This makes getting things done for a project challenging since a team that needs to do work for your project might not think it's important and might not be able to accommodate your needs. It's a pretty competitive and political environment. There are people who will take credit for your work (since they are looking for their next promotion) so make sure your keep your manager informed of what you are working on. Most teams don't get it right the first time so make sure you get everything tested.