Pros
Amazon as a company is growing rapidly. It's going into new markets and challenging big players as well as innovating in markets where it's already quite ahead. There is no dearth of choice when you are working at Amazon. There are a number of teams working on different products across all sorts of areas. The best part is that the work which you do will get shipped. That's the main thing which I love about Amazon. Software you write will see light of day in say 6 months. That's how quickly things move here. Teams are small and ownership is more. Process is lightweight and will never hinder you. I have never been asked to fill in time-sheets or made to give hourly estimates. People are friendly. Technical arguments are settled based on data and with respect. Amazon does most of its development in Java and uses a lot of open-source software. This frees engineers to focus on problems rather than re-engineer software which already exists. Although some teams have poor work-life balance, the ones which I have worked in had no such problems. I have been able to do a 9-5 on most days without any work carrying over to the weekends.
Kontras
The rapid growth of Amazon and increasing head counts have put a lot of pressure on the buildings which house Amazon employees. Many Amazon buildings are packed. Seating is cramped and elevator rides can be too close for comfort. Career growth is hard. Starting developers enter at SDE 1 with a clear path to SDE 2, but from there on out it's hard to get to SDE 3 or above. Employees on immigrant work visas like H1B should know that Amazon does not start your permanent residency process till you hit SDE 2 (level 5). This is where sometimes politics rears its ugly head. You might find really hard working engineers play the game. Amazon does not give you additional perks if you compare it with companies like Microsoft or Google. Apart from the 10% discount on Amazon purchases (capped at $100) and few team outings you won't get much. Don't expect to get the latest Amazon gadgets for free.