Avantages
The pay is (or can be anyway) good as a software engineer. The company is huge and has pretty good internal mobility. As long as you don't land on a low performing list, you can try all kinds of things on all kinds of teams. The location is right in downtown Seattle and is easily accessible on foot, bus, or bike. They also have great bike facilities in their new buildings with secure indoor storage, charging stations, and showers. There are plenty of opportunities to get experience with all the Amazon technologies like AWS, etc. at scale and addressing real and interesting problems. You also can get in on internal betas of new products (this isn't always exciting. A recent opportunity was beta testing more ads in your prime video.)
Inconvénients
Which team you join makes a huge difference. Talking to a dev from the team and asking smart questions will go a long way to determining what kind of experience you have. Almost all teams have pager duty. Some teams have absolutely brutal pager duty with alerts all hours, weekends, and holidays. Some teams have absolutely terrible management culture compounded by being understaffed (because who wants to work there). If the whole team just quit or there are 10-20 people under one manager, go find something else. Nothing is ever really done (unless it's cancelled) or to high quality, for many engineering personalities this can lead to work consuming your whole life. Amazon invests as minimally as possible in infrastructure so a lot of things are poorly documented, broken, incompatible, etc. Relative to other companies they also invest pretty minimally in project management. A lot of your job is navigating the resulting chaos and many of the leadership principals are effectively about that.