Pros
ConsenSys largely consists of a number of semi-independent teams supported by an overarching company infrastructure. The company structure is largely flat and democratic (modeled after Ethereum). Personally, this has provided me with the perfect environment to work in - self-sufficiency and independent contributions are highly encouraged. That being said, your experience may vary wildly based on which team you end up in. The company as a whole has had to evolve rapidly. While previously ConsenSys was all about building ideas and expanding on what blockchain can do, over the past year it's had to deal with growing pains and enforcing a sustainable business model.
Cons
Many of the points in the pro section could also be listed in this con section. The aforementioned growing pains have included two major rounds of layoffs within a year. I'm happy to just work with my team and go with the flow - those who aren't like me (or can't work like me) will likely find the company chaotic, confusing, and often hard to effectively communicate with. Slack is like the wild west. Free speech is encouraged but with the wide range of personalities in the company, this can often lead to hot tempers or even bullying - don't be afraid to defend yourself, it might be all the protection you get. I'm also very concerned about what I've heard about the experiences for women and PoC. Some issues include crap healthcare, marginalization and sexism.