Pros
We push the boundary of what can be done and work with great technologies. We work on solving the Amazon-scale challenged you will not find anywhere else. The company is very innovation-oriented. I have smart and enthusiastic coworkers. It is great to feel that you contributed to the success of Amazon. In my team and the teams I interact with the work-life balance is pretty good. I have time for my family and my hobbies (a little :-) ). We take turns being on call for a week, carrying a pager that week. The responsibility is great, you don't want a warehouse or the whole network to get stopped because of a bug in your service (yes, such cases happened). This is especially true during the Peak season. We write most of the software as web services based on the Amazon cloud platform using the publicly available technologies as well as some cool internal technologies. The learning curve with the internal platform is quite steep. It is great to work with somebody already familiar with it. We have lots of opportunities to work on cool projects. One can pick the areas most interesting for them.
Cons
The company is oriented towards making Amazon successful, we do not provide our technology to third-parties.