Pros
SSC has a great culture, with a large amount of expertise within the building. The HQ building itself is very nice, and there is plenty of room to grow and develop your career here. The technology is very interesting and I highly recommend joining the team if you have a chance. I have enjoyed the opportunity to do a variety of things and to shape my role autonomously to meet my own skill set. There are lots of other pros, including the ability to work from home and a decent salary.
Cons
As a startup with new and innovative technologies, there is an element of risk. This is inevitable due to the company status - if pure stability is what is needed you should work for a large prime. There is also a slightly overly hierarchical management structure, especially towards the top. Having said this, staff (including management) are friendly throughout and there is a collective sense of company identity.