My experience at Amazon has been great. I don't know anyone who cries at their desk, works 80 hours per week, or feels like they're being pushed through a meat grinder. I worked for Microsoft before Amazon, and that was brutal. You'll find bad teams at every large company. One of my friends was on one at Google.
I've had two coding challenges within that last year. One for an internship and one for a full time position (earlier today no reply yet don't expect one). The problem for me is I freeze. As soon as the "testing" type pressure gets put on I go cold and freeze. Then as soon as the test is over I can pull alllllll the information forward. It sucks because I struggle with CS exams too. Every time I have a test I freeze until I'm out of time and as soon as I leave a room it all comes back.
I kept getting calls from Amazon (Seattle number) claiming I had not done the test (which I had already done) and the HR folks mentioning I was not selected - and to try 6 months later.
I would definitely like to have another go at it, if possible.