Vantaggi
SpaceX puts interns in a position of having lots of responsibilities. They treat their interns like new hires, give them meaningful work, and push them to become better engineers. They are pushing the boundaries of engineering. They are never complacent with where they are. They are always improving things. You definitely won't be bored working here.
Svantaggi
Sometimes there is more work to go around than there are employees. This isn't necessarily a bad thing, because you don't get bored. It can lead to some stressful situations, but not anything unmanageable. Keeping the machine lean is a double edged sword, but I think it does more good than bad (for example limiting the amount of bureaucracy you have to go through, communication isn't as hard in a smaller company)