I can't post on people's walls or send them messages by typing their name on the home screen (unlike how I can send them SMS)
I can't use Facebook chat through the Messaging app
So what the hell is the point? I synced my Facebook account and was kinda annoyed since I had to import all 140-ish people, but then I realized there wasn't any point to it. The contacts I'm actually friends with (aka not just 'hey we had the same math class in 10th grade'), I can get info from them if I need to fill out all their contact info.