Pros
Forces you to learn how to grow, run projects and sort out problems independently (as management don't seem interested). Meet a lot of people that come (and then go). Free drinks on Thursdays, which normally fell on someone's leaving drinks. The US offices seem to have a good handle on projects, a plan and staff happiness (can't comment too much though). Makes the next job, at the next firm, seem fantastic.
Cons
Every waking moment. Management was unorganised at best. Lack of collective vision. Nothing worked, although that was the global strap line -Does it work? No team collaboration. Never looked after good talent people and actually treated people poorly. No training. No acknowledgment of good, hard work. Pay is way below most agencies in London.