Pros
The culture here is great! Everyone proudly sports their SpaceX gear and believes in the mission. Hours here are flexible, the environment is casual, and the people are friendly. The work is challenging, and makes you feel like you're really making an impact (and you are, because you get issued company stock). This is the perfect environment for an engineer to learn and grow. I've personally seen several promotions since I've been here, and met some extremely smart people. Perks: Free Starbucks-like Coffee and Frozen Yogurt, Subsidized gourmet meals, Cheap SpaceX swag.
Cons
The hours are long; however, no one is forcing you to stay, there is just a lot to do. Fortunately, there are several couches and places where you can unwind and de-stress when you need to. Being able to make your own hours also helps. Also, the base salary isn't as high as competitors (it's still fair), but the stock awards normally make up for it. Those who don't have a passion for aerospace technologies nor believe in Elon's vision will burn themselves out quickly.