Pros
If you have no experience in advertising, if you work hard, and if you stay for a period of time, you'll walk out with a career, based on your ability to handle and grow in a stressful environment. That's the only reason the place gets a star.
Cons
You will have no work-life balance. None. It's nearly all work, all the time. You'll make no money. None. Your raises will be from 'poverty' to 'working poor' to 'poor plus cable' to 'lower-middle-class.' I guess you could actually make money there if you stay, but that seems sadomasochistic. The people who manage and direct the units are those that stayed, those that didn't do so well in college or didn't go to begin with, and they've been warped by the experience, anyway. It's like being a new doctor, only for no money. None. HR serves the needs of the company, not the workers. You can be fired at any time, and watch out for the end of the quarter, where they unload staff so the higher-ups can make their money.