Ventajas
Thanks to a fast growth of the company and a strong coaching politics, everyone is able to improve fast and quickly reach positions with responsibilities. Especially valuable for young graduates who can then affirm themselves quite quickly professionally speaking. Some become CTO/CEO before they turn 25! As a developer, the technical challenges are also very interesting. Theodo uses the latest web technologies and make really interesting products with them. The methodology they're using definitely makes you work smartly and efficiently, which feels very nice. Finally, the environment is very stimulating. You're surrounded by smart people, who you constantly learn many things from.
Desventajas
The evolution inside the company, in terms of promotion, is very focused on how to become a CTO or a CEO, which quickly involves recruitment or sales criteria, even for developers. That can be very frustrating if your main focus is to improve your technical skills.