Pros
SpaceX's environment is extremely collaborative, exciting and motivating. The talent here is top notch and the company's mission is one that actually feels worthy of hard work. Management is extremely encouraging of growth and movement at SpaceX, moreso than any company I've experienced. They want to optimize your success at the company, so if that means taking on more responsibility or making a move to another area, you will have a ton of support in finding what suits you best.
Cons
Everyone at SpaceX works very hard and as a result, new employees might put more pressure on themselves to work long hours than they really need to, but this is something the company is improving on from the top down and lately managers have been encouraging their team's to go home at a reasonable hour.