Pros
Oliver Wyman is a great place for a recent graduate to start their career at a top consulting company. Unlike McKinsey and others, they believe in building partners out of 22 year olds. This means that by 26 you may be just as marketable as a 30 year old Engagement Manager without the 300K in MBA expenses. Four years younger and no lost opportunity or out of pocket costs seems like a win win.
Cons
They are owned by an insurance brokerage who is publicly traded. So they have two marks against them: A publicly traded consulting company has keep their shareholders happy and MMC is not a "natural" owner of a consulting company. As a result you can be growing at 20% a year and there will still be no investment capital available. These issues typically impact the career progression of staff rather than consultants.