Pros
Facebook is easily dismissed as just a social network, and the nature of the product makes it subject to a lot of critique. However, if you take a step back, it's truly marvelous that a product supports about a billion users everyday. Career opportunities are great, you can move fast and contribute, the company pays for all your stuff, the company has tons of money, tremendous job security if you make an impact, free food, tons of perks that I cannot even begin to list, great young talented coworkers, amazing lively environment (not slow, like Google), great benefits, compensation.
Cons
Engineering isn't as advanced as Google (owing to very young age and inexperience of workers), You can find messy code if you look in the nooks and crannies.
