Pros
I just started working at FB ~2 months ago, but I already love it so much! There is so much transparency from day 1, it was actually a little alarming at first. But it's awesome to get to see what everyone is working on and to be able to easily contact anyone in the company. Even though the company is pretty big, you still get the same family-like feeling of a small startup. Everyone is very approachable and helpful, so it's not at all intimidating to contact your POC to get help you need. It's a very supportive and healthy work environment! Other pros: Q&A with Mark every Friday (he is so funny and brilliant!), delicious food everywhere (I already gained 10 lbs), beautiful campus, so many amenities and perks, brilliant and kind coworkers, really fun woodshop classes, I could go on and on!
Cons
Information is not very well organized. For a new person it can be a little intimidating to navigate and find the info you need, so that takes some getting used to.