Pros
The company is pretty small still, so changes and improvements happen quickly. You get to develop cutting edge technology, working on all aspects of the development cycle (conception, modelling, testing, technical drawing, manufacture). Management are supportive and trusting of the technical team, giving you as much responsibility as you want to lead and collaborate on projects. There's room for career progression. You learn a lot of things (technical, professional, the industry) in a very short amount of time. You aren't expected to know everything, but you are expected to pitch in and get your hands dirty, learning what you need to in order to get the job done. The environment is supportive and encouraging, and your colleagues will always help you out when you need it. Given the size of the company, you know exactly what everyone is doing, including the business development team. Technical team involvement with the business development side is encouraged, but equally you can stay purely technical if you want. The technical team has a 90% retention rate since it was founded three years ago.
Cons
Nature of a tech start-up I guess, but juggling multiple projects can get frustrating when you can't spend as long as you'd like on a particular problem.