They have a culture of overwork and moving fast. I was looking at job postings for SpaceX & Tesla a couple years ago, and every single one of them explicitly mentioned that you will be expected to work more than standard work hours and put in time on weekends, which is very different from all the other companies that stress work life balance. I'm sure it works for a lot of people, but you should be sure of what you are getting into. And I don't expect employees will stay happy if/when the Musk stock rally stops.