Pros
SpaceX is an exciting place to work. Elon Musk has the courage and funding to do what people were saying for decades--quit tweaking 1950s technology--and combine lessons from the past with cutting edge manufacturing technologies. Lots of incidental perks, from a really good on-site restaurant to fancy coffee machines. The software challenges are probably just about right for many engineers and the corporate goal of Mars settlement is one that could change history.
Cons
Not really Cons, just caveats. It seems as though many people find the programming challenge given to job applicants hard. It seems to be a fairly good match for the difficulty of much of the Flight Software work, so if you don’t find it especially hard, and complete it successfully well before the deadline, you might not find the work as challenging as you hope. If you are a participant in open source activities, ITAR (International Traffic in Arms Regulations) makes for a huge hurdle. Hours expected are sometimes long enough that some people nap at their desks. Most of the software developers are pretty junior. Glad I read other reviews because it gave me a pretty good idea of what to expect.