When overriding the registration controller from devise, is it possible to access the newly created

I don't know how you have your application encapsulated or even what
you consider behavior but if it were me I would skip trying to be
clever and skip trying to override methods I have no business being in
and simply hook into creation on the model:
http://api.rubyonrails.org/classes/ActiveRecord/Callbacks.html --
http://api.rubyonrails.org/classes/ActiveModel/Callbacks.html just
because it's tied to the database does not mean it's strictly an
interface between your app and the database ;).

There is a resource object about that should have the newly created user.

Check out:

http://stackoverflow.com/questions/4702806/how-to-add-callback-after-registration-with-rails3-and-devise

This methodology worked well for me.