This looks amazing. It appears to have absolutely everything I need. For $150 I'm willing to give it a trial. I'm currently using Pancake (http://pancakeapp.com) which is also self-hosted, so I'm fine with that. Duet makes me feel bad for Pancake already because if it's as awesome as it looks, I may switch my billing over...provided one thing...

Because I work with an agency, I'm typically billing my client, who then bills their client (plus markup). Obviously we don't want their client to see what I charged them. Is it possible to "hide" the billing for certain users?