Pros
If you're looking for work with meaning then it probably doesn't get better than SpaceX. You're lucky to be working at one of the only companies really shaking up the industry. We don't just talk big, we make it happen. Lots of people are super driven here. If you're highly motivated and ambitious then you can accomplish a lot at SpaceX. No one is going to stop you, there's way too much work to do.
Cons
With so many highly passionate, driven people, tensions often run high. People will defend their points of view, you'll defend yours, and it's tough keeping your cool. Picking which battles to fight and which to let go. The overall mission does help us keep perspective, but on a personal level it is non-stop ups and downs. You watch people hold on until they get fed up and flung off. Also people work a lot here. Not because they have to, but because they want to. Space is cool, being a part of it is cool. But it's easy to overwork yourself without knowing it. This plus the above can lead to quick burnout. Personally I'm continually riding the edge of what I can handle, but I'm driven to a fault, that's the kind of people here.