I'm hearing a lot of good things from some pro WGA writer friends of mine about Script Studio because of its ability to outline and structure. I checked out the demo and like what I see so far. The dual dialogue function is the best I've seen. It used to be called Movie Outline but was relaunched with a new look and name last year. It's a bit pricey for me right now but I might buy on Black Friday if they run a deal.