Pros
I was always hesitant about working at Amazon but have been pleasantly surprised by how much I'm enjoying it. I love that it feels like a startup environment (nimble, innovative, thinking big etc) yet we have all the resources and support that we need to be successful. Really enjoy working with incredibly smart people. Everyone is super organized and efficient in their work styles. Also love the writing culture - pushes everyone to put their ideas down on paper so that meetings are run highly efficiently. I also love how their leadership principles are ingrained into everyday working behavior. I've never worked anywhere where everyone actually practices the principles the organization stands for, on a regular basis. If you are a top performer, you will thrive here!
Cons
There are so many teams doing so many things (and some initiatives are very related) - difficult to keep track of what's happening. It is a giant company so there are internal processes that are frustrating to deal with (though still fewer than anywhere large I've worked at before). Amazon builds most of its own internal software, which is annoying to use sometimes.