I was presented with two choices; Public (recommended) and to keep the current settings. I like the way my settings were, so I kept them. I'm looking at the privacy page right now and the ONLY difference that I can see is it wants a password to access the privacy settings. Everything underneath is exactly the same way it was before they made their changes, which BTW are Everyone for adding me & my location with everything else locked down to "Only Friends". If something's changed under there, I can't see it.
Now, it's pretty sneaky of them to call it a change and put up a big screen with just a few choices that are defaulted to Everybody. Still, I don't see where it's irrevocable; surely they learned something from the Beacon fiasco.