Pros
Ipsos attracts really smart people, and my division was full of both smart and good people. Ultimately, I remained at Ipsos longer than I should have career-wise because I enjoyed the work and loved my colleagues. If you start your career here, there will definitely be room for you to learn and grow your career over time. They offer terrific training (Ipsos University) as well, which is there for the taking.
Cons
Compensation is not great compared to competitors (and certainly not compared to corporate/client side). The culture and general management has been suffering since the Synovate acquisition--rather than what made Ipsos great helping to make Synovate better, the ills and weaknesses that plagued Synovate have bled into Ipsos. While this varies by division, being a matrix organization, the company generally (and certain divisions specifically) is blind to this infection and struggling to stay on track performance-wise as a result. If you move to Ipsos mid-career, be prepared, you may likely find that room for growth will be limited...exec level positions tend not to open often and, when they do, too often are filled by outside hires than inside promotions.