Of course, Final Draft devotees may say the same thing about FD it's maybe what you're used to that counts. Swapping fretting about formatting styles for fretting about your writing app is obviously no progress at all, and my experience is that Screenwriter is a bit less noticeable in use than Final Draft. 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).