Amazon

Couldn't ask for a better mentor, manager, or teammates. They gave me a perfect intern project--very enjoyable to work on, raising many interesting algorithmic questions, and very relevant. Mostly, it was relevant to what the team would be doing in the next year, so there wasn't too much pressure. They were consistently supportive and encouraging, no matter how often I pestered them with questions about how exactly my project would be used and feedback on API decisions. They were extremely generous with their time and never made me feel like I was taking too much of it.

Work/life balance was quite reasonable for the people on my team. You'd have to work much longer hours in places like AWS, but people generally know what they're getting into. It's nothing like the NYTimes "expose" in 2015 would suggest.

Introverts may find it difficult to meet other interns (as I did) at the very large events designed for this purpose, where it is easy to feel lost.

My one con seems inevitable given the huge intern body, but it's possible they could have more structured events for meeting other interns.