We are using this method on our site. Create temporary user on the fly and let the user overwrite it if they select to save their state and it works great for u

We are using this method on our site. Create temporary user on the fly and let the user overwrite it if they select to save their state and it works great for us. I think just by renaming the registration page to save work page gives you an advantage since the users are sick and tired of having to register in order to get any value.