Edit: oddly iOS 7 hasn't autoinstalled this yet.
I moved all my non-critical stuff over (to test it out), saw the Google Authenticator update, and then had to go and reconfigure those accounts anyway.
I highly recommend making sure your backup phone number is updated and verified and/or you have backup codes prepped.
Duo seems to be quite nice, I doubt I'll end up using the backup codes.
Incidentally, GitHub has it right - "download a text file of your backup codes" is much easier than "print this page nad hope you don't lose it"; I find find(1) outpaces my frantic drawer-emptying.
That is odd - it installed several hours ago for me.