Pros
Exposure to planet-scale services with a very high bar on reliability. Your work literally has impact on the rest of the world as many other companies build things on top of the services you own. Full ownership (from design through carrying the pager) teaches you to think ahead and avoid cutting corners. It's relatively easy to move within the company if you want to try something else. Compensation is pretty good.
Cons
Too much operational work, very slow promotion process (it's normal to see people stay at one level for 5+ years despite doing good work), unreasonable assumptions around on-call rotations that sometimes cause whole teams to implode. Internal tooling is powerful but very difficult to use and might make things seem very complicated if you already have experience using standard modern tooling. The extremely competitve market Amazon finds itself in often results in things being shipped before they are ready. As those services start scaling (typically there is a huge demand for them) the operational side tends to get out of hand with too many people running behind the curtains to keep the lights on, while fixing the underlying core issues remains out of sight. My personal observation is that (largely due to the reasons outlined above) most folks who already had relevant work experience before joining Amazon tend to not stay for too long - typically 1-2 years.