Pros
Working on the most sophisticated rocket booster in human history is a remarkable experience. Watching the Falcon 9 perform on launch days provides workplace motivation that is hard to imagine any other company on earth duplicating. The overarching goal of colonizing Mars sounds ridiculous, but it is the genuine long-term strategy of this company. Hard to imagine a better reason to get out of bed each morning. Playing such a direct role in one of the most important initiatives in human history is something I'm proud and humbled to experience.
Cons
You don't get all those pros without some sacrifice. Work/life balance can be difficult in a lot of professions, especially if you're naturally inclined to work hard (i.e., workaholic), and SpaceX is no exception. The stress of working here has been greater than in my various past positions with other companies, but it is not enough to deter me from continuing my career here and is greatly outweighed by the pros of knowing how I am directly contributing to the human species.