I did. It basically syncs with your Facebook account and checks all the friends you got in both your iPhone and FB, then adds the info from FB (birthday, pic, etc..) into your contacts app on the iPhone (unless you already have such information).
Also as far as I know, it doesn't delete any info you might have of your contacts on your iPhone. Also doesn't publish anything on your timeline. It's good to get that extra bit of information on your contacts, if you ask me (in my case it added a ton of birthdays on my calendar which is nice, and you can toggle on/off).