Pros
Stellar Science is a wonderful place to work for software developers dedicated to their craft. The staff is top-notch, and will push anyone to improve. The organization is very flat. I am not alone in having worked on one project as the lead, and another as a worker bee, where the other project's lead was one of my project's worker bees. The company tries very hard to keep employees happy. Performance reviews are as much about you reviewing the company as them reviewing you. Your desires about the type of work and kind of projects are taken into account when assigning your work. They can't always create a perfect match, of course, but they do make an effort.
Cons
If you want to climb the corporate ladder, this isn't the place. This is not a typical stove pipped organization with department heads and layers of management. You are expected to be self motivated. But are those cons? It depends on you.