Vantaggi
Flexible hours, smart approach to work - do your work whenever, wherever, as long as you do it well. No politics, no rigid processes or hierarchy Fast-paced environment, smart and competent people. Easy to bring up ideas and see them develop into actions quickly. Nice office environment, some kind of sport/activity available practically every day. They care about their employees - set up online training courses, ran several HR surveys, have accommodated a lot of employees' wishes/constraints to work partly from home, to take long trips, to study, etc.
Svantaggi
The usual cons that come with these informal, ambiguous environments - no clear reporting line, you need to be proactive and ask around. No HR department, so you have to take matters into your own hands and manage your career evolution. Not always enough communications from the leaders on strategic direction but you can tell they're working on fixing it.