Ventajas
Amazon is a great company in many respects -- the core retail website and Amazon's customer service operations are outstanding. Given it's established status as a successful online retailer, it's in an advantageous position to sell digital media which will of course become an increasingly huge market. The company also has an extremely driven, hands-on, engaged CEO.
Desventajas
The management style in many departments is almost comically top-down. As a result, it often feels like Amazon hires a lot of smart people to perform tasks that don't really have a lot of strategic significance -- a lot of tactical decision-making gets made at a very high level. So while everyone is working really fast, things tend to happen slow. As much as anything, I think this explains the very high level of employee turnover at the company.