Pros
As a subsidiary of Marsh McLennan, you have the opportunity to grow a long career across the operating companies through savvy networking and exposure. There's a an emphasis on just-in-time learning, informally and formally through on-demand video training and townhalls, etc.
Cons
There is a lot of 'who-you-know' as the basis for opportunities, thus a lot of subjectivity on who gets promoted and why. You will need sponsors and advocates to get ahead. There's an overemphasis on credentials as a proxy for performance, and a lot of too-many-bosses-and-not-enough-workers in certain divisions; also the phenomenon of the company performing well financially, but raises being paltry. Certain divisions/practices are insular and act like they're a company unto themselves.