I'm looking at this integration too. Friend Connect and Google's OpenSocial should also be considered. Gigya appears to use a proprietary authentication, but OpenSocial is "open."
Not sure I need integration, but I want to get to the point that users can initially "join" through Open ID, but somewhere they are prompted to complete additional fields (I know, upcoming feature). Would also like to have different additional fields be presented depending on "user type" requested (e.g. subscriber, contributer, business, consumer).
Open Social has good docs over at Google Code and custom fields plugins DRegister and Register Plus appear to be abandoned.