I've recently been chosen to do (read: roped into doing) the DV work on a project that I'm involved with. None of us has any substantive DV experience, but we all (read: they all) decided that a project we're working on is best served up on DVD. As the only Mac user, I was tapped to do the editing and authoring. So, I would be able to get DVD Studio Pro paid-for if I really need it. But, never having used DVD SP (or, really, iDVD for that matter), I'm not so sure what SP can do that iDVD can't. When does one really need to fork out for DVD SP?