Pros
Creating cutting edge software in a new and burgeoning field. If you're used to a big and nasty corporate tech company, this one is still a baby, so it's teeth aren't that sharp yet. You may find this as an opportunity to get on the corporate ladder now before it's too late. Though it's still a fairly liberal and progressive company where the employees still want to "do the right thing" ...
Cons
... the management increasingly doesn't want to get caught "being evil". Very few of the original creatives and technicians still work at the company barring the very few at the top of the core. Corporate pressure has replaced virtually all of people who brought Unity into fruition as it lumbers its way into the big leagues as a corporate juggernaut. The company is now more interested in KPI driven pseudo-goals rather than intelligently focused achievements. This leads, not to a meritocracy, but to that typical corporate bullying and power taking that is seen in all big companies. Perhaps this was inevitable.