Google has been working with Plaxo and Facebook to improve the registration success rate for Gmail users. We now see success rates as high as 90%, compared to the 50-60% rate that most websites see with traditional registration mechanisms. This result was achieved using a combination of our OpenID, OAuth and Portable Contacts APIs. While those APIs have been available for over a year, we have added a number of refinements based on our experience with Plaxo and Facebook.
For any of your readers that are looking to implement OpenID to facilitate registration, login, and rich user profile creation on your websites, check out the OpenID Foundation website at http://openid.net/add-openid/