Maybe I'm being naiive, but I don't get what all the fuss is about. They can't see the content of your messages. Who cares if Facebook have your IP address, or know your battery level, or how often you use the app and for how long? To be honest, I'm suprised facebook didn't already have this information seeing as they own WhatsApp.
I get that some people like to be as private as possible, but what data specifically are people concerned about Facebook now having that they didn't previously, and why are you concerned about it? It's a genuine question, I'm not trying to provoke!!