Pros
Creative comes first, and it's top-notch. Blue-chip clients: where else can you work on IBM, GE, Converse, Nike, Pepsi, McDonald's, Motorola, Harley-Davidson and Target in the course of a few years? Talented, hard-working, professional people. You'll learn a lot from your colleagues. Freedom to be yourself. Relaxed work environment. Personalities welcome.
Cons
Very little transparency. Major changes are announced suddenly via email. Employee feedback on these changes isn't really solicited—let alone input before the changes are made. Work-life balance, though improved in the past few years, is still heavily tilted in favor of work. There's not much of a career path or mentoring to speak of. You'll learn a lot from doing the work, and working with smart people, but you're making it up as you go along from a career development standpoint. (This is especially true if you're not a designer.) Internal knowledge-sharing is similarly ad hoc. Compensation and benefits are average for the industry. PTO is use-it or lose-it and does not carry over from year to year. (On the other hand, the office is usually closed the week between Christmas and New Year's, and not counted against PTO.)