Pros
You will learn the basics of the retail advertising business at this giant agency. If you apply yourself and suffer through, you will walk away emotionally disturbed yet with a lot of bottom tier industry knowledge and ability. Don't get me wrong: you won't walk out of this joint with the ability to create a brand or launch a national campaign you can be proud of. But you can get a better job up a few rungs on the ladder. Added bonus: since 90% of the people there are also poor and abused by upper and middle management, you'll have a lot of casual co-workers to commiserate with.
Cons
There is no sharing of the wealth here. None. A ton of people work lawyer-long hours for basically no money (less that $25K, with a 'middle class' salary being $35K or so. Seriously.) All that work makes ten people at the top very, very, very rich. You could start an Occupy Zimmerman movement. The turnover is insane at the agency, much more like working in a fast food restaurant than an office of college degreed people. As a result, you're constantly churning through new people and new work relationships, there's little consistency, training and stability to your work day (beyond the stable environment of being worked to the bone for no money.) For those who do stay and progress to lower or middle management and salary positions, they have a financial incentive to toe the company line from the top: so its very much trickle-down horror through the agency. Also, since the place has such high turnover and true talent, intellect and ability vacate as soon as their sentence is up, you have to wonder at those middle-level people who have stayed and made a career there. What exactly are you going to learn from the people who can't find work anywhere else? Who are the people made happy by working here, and do you really want to be working with them or for them? (For many people, the answer is obviously "no.") From the "salary freezes" (which never apply to ownership,) to the insane hours for no money, this is really a wretched place to work. It's the Wal-Mart of marketing, and it should be a job you take when you have no other alternative.