I have a new iPhone 5 and I tried to connect to my Google account, but without success.
I first open the Accounts view:
When clicking on Google, the OAuth view appears and I enter my email/password.
I immediately receive a security alert on my Gmail indicating that a new device is trying to connect to my account. I click Check my activity and confirm that I'm at the origin of this connection.
Unfortunately, my iPhone goes back to the Accounts view without adding my gmail account to the list.