Pros
Treated like a real engineer
Great team dynamics -- I feel like I'm a part of my team and actually contributing to their work
Awesome, cheap food and free coffee bar with great, friendly baristas
I'm held constantly accountable and have complete ownership of my work -- I was thrown at a project on a really crazy cool part of the rocket, and now I am the expert on the part
Lots of exposure to technicians on the floor -- I spend ~50% of my time with techs.
Very open company culture -- you can read almost anything going on in any department just by being on the SpaceX intranet. It's super easy to get information, get what you need
Ability to ask lots of questions and explore different groups is great -- if the group you intern in isn't necessarily what you want, you can come back to a different group no problem and this is encouraged rather than looked down upon
The mission is everywhere, and everyone from front office engineers, to technicians, to facilities staff is super excited to finally get to Mars
Limited to 50 hr/wk as an intern - I usually work more/about the same as the full-time employees on my team. I like the opportunity to get 1.5x overtime, but by no means is that an expectation.
Shuttle to work from intern housing
Cons
Intern housing is not great-- it's just an ok apartment for a fair sum of money. The contract they have for this housing is ending soon and I know it is under review.