Pros
Salary was better than other agencies I'd been at or heard at. Only slightly though
Cons
I don't want to sound negative, but this was genuinely the worst job I'd ever had. I cried so much in the first few months working there and eventually just became so defeated and cold and detached in order to get by. My partner was genuinely worried for me.
I was on the Verizon account and the clients treated us horribly and didn't care how little time they wanted revisions by--leading to insane work hours. From the Ogilvy staff side, I had overheard folks saying homophobic remarks in the halls, creative leads who talked down to us regularly, and insults rampant. I've genuinely never experienced anything like it and it knocked my confidence so much.
I also don't think the Ogilvy name means anything these days. Clients don't care, other agencies don't care, and from my experience, smaller agencies do better work and have better culture anyway.
During my time there I met a number of people who said they loved Ogilvy and wanted to stay there for as long as they could, so I think some other people have different experiences. Maybe they just got lucky.