Pros
You'll be working with the best. These are people who not only are veterans in the industry, but have been significant contributors in the industry. It's a quality vs quantity type of crowd. You think you're good? This place will humble you down. Everyone's brilliant (even the interns and juniors).
Cons
As with any fast-paced environment, you have to be willing to be agile and change fast. But at the same time, you need to stand your ground at what's right. There are certain directives that make you go, "what the hell?" I think only the strong in this company will survive. If you are used to being pampered or spoiled by a corporate environment, you're going to cry here.