Pros
The aim of the company is to ensure the continued survival of the human species by making us multi-planetary. It that doesn't get you excited...check your pulse... You get to work truly hands on with cutting edge technology. You are surrounded by incredibly smart and driven people. You are given complete ownership and responsibility for your work. You get to contribute to an endeavor that only nation states have previously accomplished. You also get to accomplish world firsts. I had tears in my eyes when we landed the first booster!
Cons
There's no such thing as a free lunch. With the outrageous pros described above come equally outrageous demands and stress. These do not come strictly from Management. They are primarily self created by the superstar type A's who work there. See if you can't read between the lines on some of the negative reviews that the person is basically saying "I'm awesome and I couldn't handle SpaceX, therefore SpaceX must be broken"... If you work only to live, and are looking for a 9-5. THIS IS NOT IT! If you really believe in what the company is trying to achieve; and are prepared to make some personal sacrifices to ensure they do. Welcome to Nirvana!