Pros
Great company name to have on a resume, especially in communications fields. Attracts great talent in its field, less good at keeping them. Big name clients across a wide variety of industries. If you're looking to build a career in a communications field this is a place to be, limitless networking opportunities and there's always something interesting going on around the office. Experience as an employee varies widely between teams but if you're lucky to get a good manager the work is relatively simple and many teams allow even junior staff to be self directed and get good experience fast.
Cons
While the Ogilvy network has found continued success especially when it comes to industry awards, the actual quality of work coming from the New York office is lackluster. Morale across the office is incredibly low and almost no one seems genuinely excited about the work and any sorts of positivity from management generally ring false and feel like canned employee engagement bs. Main problems are: poor pay, lack of transparency in promotions, poor leadership, and absence of Ogilvy generated industry thought leadership. The salaries are competitive somewhat with the rest of the industry but for a financially independent person in NYC they can make it difficult to make ends meet. The main issue is that raises rarely come and no one knows how to get a promotion (hint: hang out at the bar next to the office). Ogilvy did a North America wide survey a year or so ago that found 75% of employees believe their advancement opportunities are neither laid out for them nor are they awarded based on merit. To me that sums up the way the company works. Senior leadership is completely uninspiring, the chief creative officer lives in a converted 19th century firehouse in NYC and tweets things like "rules are what the artist breaks". Though it pays lip service to founder David Ogilvy, the agency was bought by WPP, against much protesting from Mr Ogilvy, in 1989 and these days it is rarely a partner in the work and more an executor of whatever whims the client has. The only accounts keeping the lights on are American Express and, most of all, IBM, both of which suck up resources across the building especially when it comes to talented staff. If you just want an easy job that you can leave at 6pm this is the one, but if you desire anything deeper from your work or a company that cares about what it creates, keep looking.