Pros
AOB is a really good place to grow your career if you have good experience but are looking for a chance to be more involved since it is still growing fast and you will get to wear multiple hats.
Excellent work environment- good kitchen, good resources, and admin stuff is well run
Great executives who you can learn from
Get to work with very high level clients like Slack, EA, Kabam, etc.
Good opportunities for going to industry events/conferences/parties
Good culture- people really like each other/go to lunch etc.
The product is innovative which is important if you are looking to work for a company that is changing how technology is used, not just trying to make money by copy+pasting an existing platform
Cons
Business model has fluctuated making it hard to know what is most important for the company's success- for example you could be working on a project and find out it is no longer relevant- but that is pretty normal at a Series B.