Avantages
Amazon has a great engineering culture and lots of people of quality, which makes the work interesting. There is no shortage of things to work on, and it's possible to see many different things while staying in the same company. Though not perfect, hiring and promotion processes are fairly transparent and do their best to be based on merit and objectivity. Overall, the company has a lot of energy and insatiable ambition to do more, which is both scary but impressive.
Inconvénients
Like all tech companies, and maybe even all american companies, I'm not a fan of the wave of political correctness that is diffusing through the culture and tarnishes the otherwise very open cultures of expressing the ideas you truly hold and think are the most valuable to drive decisions. In some locations, pay may not be the best of the market (they strive to stay somewhere around the 80-90th percentile depending on how competitive the market is, so I heard) , and Amazon's frugality also means fewer perks compared to other big tech companies.