Pros
Stratolaunch is the place to work if you want to contribute to reusable hypersonics. The challenges are novel. The people are professional. You will meet many personality types. There is a distinct sense that management cares about you because they communicate well and the benefits are very well put together.
Cons
There is some overtime because of schedule pressure, but thus is the nature of aerospace startups. Overtime is usually paid. All onsite work occurs in Mojave, and while management tries to allow people to work from home, this is often not possible. This is a major drawback as it is difficult to meet new people when living in Lancaster / Tehachapi / Mojave. Software work can feel somewhat isolated from the rest of the company because the product is not software.