Pros
SOE brings opportunities to work on projects that match your interests and passions, which can be a very rare thing to find in an engineering field without starting your own company. The variety of work is a dream for a generalist, you can work in all the disciplines you enjoy. People are very transparent and personable, and there is a good balance between an overtly ridid structure and a completely flat company. I've found it's always possible to talk to the people you have questions for, and many are very receptive to new ideas. Company culture encourages learning, not overdoing it/burning out, and getting things done by working smart and leaning on each other. The office tries to support a reduced stress environment, meals are provided, there is a quiet room, and an open pet policy.
Cons
It's got small company structure but has grown to be medium sized too quickly - internal processes are still in flux and thus you may not settle into one way of doing things (this is changing, albeit slowly). Some projects are much more demanding than others and it can be easy to feel pressured to work late, even if that pressure is mainly internalized. They generally run a lean operating budget, while there are perks the office and amenities there are utilitarian. There could be more opportunities to learn and research in idle time, but the structure isn't there to support it. The office is in an office park which is car-centric and not very fun to exist in. some food is walkable but across big roads w/ lots of car traffic.