I discovered this morning that the [Google Authenticator app] is broken in iOS 7. While it does display authentication codes, it doesn’t display the associated service description. So unless you only use Authenticator for a single service, you’re kinda stuck.
Google [are aware of the issue], but haven’t yet released a fix.
Urgently needing to login to Amazon AWS, I discovered an alternative app called [Authy] that _does_ work on iOS 7. I was quickly able to get setup with (the better looking) Authy and Amazon AWS, Google and Dropbox, and subsequently deleted the broken Google Authenticator app.