The only point of a screenwriting app is to get out of your way. Screenwriter's strengths are, first of all, in its transparency. (Celtx and Montage are both coming along, but I'd not yet trust real live work to them. It's not without its frustrations but I find it a more robust and congenial tool than its only real rival, Final Draft.
Been using Screenwriter for many years and v6 is a big jump ahead of the previous version (Screenwriter 2000).
