Pros
SpaceX's bold and inspirational mission along with already having very impressive accomplishments got my attention in the first place. What I didn't realize until later is how incredible it feels to contribute to some of the most amazing engineering accomplishments of our time. I work on the flight software engineering team. The team is exceptionally talented and helpful. Because we're co-located (all engineering is mostly on the same floor of one building) communication is effortless - just walk over. Access to information and production facilities is top-notch and there are very few impediments to getting things done as compared to other places I've worked. When trying to get help with something I'm new to I never hear "I'm too busy for that, send an email to my manager" - people will put aside what they're working on to understand your problem and help you get on the right path to resolving it. I've never felt so productive until joining SpaceX. We do work long weeks (50-60 hours on average, not crazy) but it is almost always self-imposed - you feel empowered to and responsible for achieving your own goals despite emergent work creeping in. Even though we work hard people stay very professional and courteous - it's not as stressful as one might expect and the feeling of personal accomplishment goes a long way. Mobility within the software engineering organization is encouraged as is learning new skills and continuously challenging how things are done. In this kind of environment you can grow exceptionally fast. The projects here move very fast and you will have a crucial impact on everything you choose to contribute to. You will not be bored.
Cons
The Los Angeles area is expensive as many sources can confirm, and the commuting experience can be unpleasant depending on where you live. The immediate area is mostly industrial so living close to work is generally out of the option.