Pros
This is my second engineering job, and I know a lot of engineers at other companies. Spacex offers far more responsibility and opportunity for significant input early on in your career. New engineers are designing new parts that will go on rockets launching in less than a year. No one is going to spend months designing a bracket. Major projects generally only last a couple years and then you have the opportunity to work on something new. I can't imagine another company that will develop your engineering skills/knowledge faster while also giving you the opportunity to making a significant contribution to the science/engineering world.
Cons
You get out what you put in which requires taking a lot of initiative and independent working to be successful. In engineering, job descriptions are not always well defined which can lead to poor career development if you aren't actively presenting good ideas. Fortunately there is plenty of freedom to be vocal and let your thoughts be heard.
