Pros
I've been an engineer here for over 3 years now. Nowhere else will an engineer have as large an impact as here. Interns and new employees will be working on important projects right away, and you will see your project launch in months rather than decades. The turnover rate is not as bad as some reviews make it sound. Everyone that I know that has been let go has been given a legitimate chance to turn their performance around. I consider this a pro, because it makes my life harder when I am working with people who don't care about their work. Everyone at SpaceX cares about what they are doing
Cons
Yes, it is a lot of work. If rockets were easy, everyone would do them. If you want to read a book while at work all day, work somewhere else. Having said that, it is easy enough to manage your time once you get settled in. It is difficult at times to find the correct work/life balance, but that is based on the individual