I'm in the process of setting up the registration add-on and I've noticed a few gotchas.
1. I register a user, everything works. I then delete the user. When I try to register that same user I cannot use the same email again. For some reason gravity forms keeps the email in its table.
2 .So I choose a different password. When I go to the profile most of the user fields are not populated. First and last name, website, bio, etc.. are missing.
3. When a user makes an error in the registration process the password fields look like they are still filled in. But when the user corrects all errors and re-submits, an error for the passwords being incorrect stops the process. So you must re-type the passwords.