Pros
SpaceX is a small company in comparison to its monumental achievements. This comes from a fast paced environment, a cooperative corporate culture, and excellent hiring practices. I have found people are more interested in doing than talking and are committed to a 'best ideal wins' philosophy. Also, people are extremely passionate about what they do - they are genuinely excited to teach you about what they are working on; they want and need help so it is to their advantage to make you a stronger team member. The small perks that come with working for SpaceX are also a bonus - on site barista at most locations, complimentary food throughout the day. Oh yeah... you get to work with rockets.
Cons
There is definitely pressure to succeed but it is acceptable and not as severe as I was warned.