Betternestedset talk - May 2007 - example controller and one question

hi there,
I started using better nested set, however there are things that  
aren''t too clear for me.
I''m in the process of building a small interface to manage a simple  
Category model that can have multiple roots.
I''ve tried to scope them but I got strange errors, is there anybody  
that can provide a sample controller to manage categories?
Also, I need to display the whole Category tree, I''ve tried to look  
at full_set and helper, but I really can''t find an answer.

Thanks in advance for any hints.