Overall: The Amazon interview process is not for the faint of heart. It's difficult and long. It's meant to weed out people who are not alpha or type-A employees. I was told many times that Amazon is a very unique environment that not everyone is built for which is why they have a very high turnover rate (this was word-for-word told to me by an interviewer).
I've interviewed twice at AWS and in my last interview cycle was I was moved forward directly to the Loop (final) interview because the hiring manager felt I was a good fit for AWS and the role. The Loop is essentially 5 interviewers talking to you for 45 minutes each. My Loop was scheduled all on the same day. I'll also add that for roles requiring 5 years of experience or more you will have to complete a writing assignment prior to your final interview.
Pros: My recruiter gave me all the information and guidance I needed to prep so there was never any point where I felt like I was walking in blind. I felt confident in what I needed to know. As referenced by other reviews here, you need to know their leadership principles and have 20 examples ready to talk about in the interview. They need to be presented in the STAR format with lots of data points. They are a data-driven company and want to see you can understand how to analyze data. The interviewers I talked to were really nice and transparent about the role and interesting to talk to. I felt they really were taking the time to listen to what I had to say. Overall, I felt my Loop was enjoyable even if it was very much a marathon.
Cons: I was working with Amazon/AWS for two months on this interview process. The holidays were in between but it was a long process to just get interviews scheduled. I prepped for an entire week for the Loop. I found it intense. I also had a writing assignment which for me took several hours to complete.
My biggest complaint as a candidate is that recruiting really dropped the ball big time with me. Amazon is known for and will tell you over and over that their candidate experience is very high standard. They strive to give you a good experience (because more than likely you're an Amazon customer). I did not experience this. I was passed from one recruiter to another without explanation or that recruiter reaching out. After my Loop, I was told numerous times I'd be hearing back from the recruiter via a phone call to see if I would be getting an offer in 5 business days. I never heard back from anyone in that time frame. I emailed my recruiter twice and never received a response. It wasn't until I emailed the hiring manager (luckily we were connected on LinkedIn) to ask them what was going on. It was only then that I got a phone call 10 days later from recruitment saying I didn't get the role, but the recruiter sounded super disorganized and clearly had forgotten about me as a candidate. Not cool. I was really annoyed about that. It felt very much like I did not matter now that they didn't want to hire me.