The organisation is chaotic. Working here feels like a constant state of crisis. People pulled onto projects to fight short term fires. Never ending anxiety and urgency. Saw far too many good people burnt out and chewed up by working there. The company seems almost proud of this - 'well, you are at Uncommon!' For this reason I probably wouldn't recommend a job here - even though I enjoyed it - unless you're good in that kind of environment.
I was in the London office - but from what I hear the New York office is even more chaotic.
Secondly (and this is a pro and a con!) Uncommon's priority is building its own showreel. This means they're really focused on making great creative work, but it also means they define great creative work as 'work that looks good in our portfolio'. There's sometimes contempt for other agencies/clients/the idea of marketing and advertising. This means reasonable client requests are sometimes completely disregarded - often leading to tense relationships.