Pros
If you are fresh out of college, Amazon can be a great place to pick up loads of skills. You wind up (mostly) managing your own projects end to end, so you wind up learning about build, deployment, system administration, schema design, as well as any coding required for the task. You also learn about scalablity. And of course, you get to work with lots of cool distributed technologies. There's something to be said for having software that runs on hundreds of servers. There are a few nice perks as well, such as a free bus pass and occasional keggers. The environment is pretty relaxed in that you don't have to dress up or watch what you say.
Kontras
You get a pager pretty shortly after starting and are expected to respond to it at all hours. Management expects everyone to work crazy hours and thinks nothing of asking you to work weekends, nights, or even cancel your vacation to support a project launch. Cooperation between teams is nearly non-existent and you will often wind up implementing necessary features yourself. Due to political wrangling you can wind up taking on responsibilities far outside of your realm, like taking over QA's job for a spell. You are expected to provide frontline support for the databases despite your level of database knowledge. Unless you are really lucky or really senior, expect to spend < 25% of your time actually writing software - most of your time is spent troubleshooting or triaging emergencies.