Pros
Big Nerd Ranch is just what it claims, a place where some of the smartest people in the industry get there start or grow exponentially, eventually taking that knowledge to others. Developers are not just brilliant but also kind and passionate. It really has a lot to someone if they can be self directed and know what they want to achieve.
Cons
It like a power boat without a rudder. With the smartest Nerds all packed in one place things move quickly, but to where? If you looking for someone to guide you in your career you will be lost at BNR. There's a lot not said by upper management and this applies to big decisions that affect your future income. Speaking of income, your not going to get rich working at BNR. You might consider the offset of your income pays for all the knowledge you take with you when your next job doubles your salary.