Final Draft is the "industry standard" in computer software for professional scripts for movies, television, and even the stage. There are others out there, most notably Montage (but it's only for Macs and I work on a PC) and Movie Magic Screenwriter, and a bunch of free programs, such as Celtx, FiveSprockets and Scripped. I prefer Final Draft -- it's very easy to use and it has a lot of excellent features. And did I mention that it's the industry standard? Many professional screenwriters in Hollywood use the program to create their scripts -- Oliver Stone, J.J. Abrams, Darren Aronofsky, Alan Ball, Ben Stiller, Stanley Tucci, Terry Gilliam, Steven Bochco, Sofia Coppola, James Cameron, Wes Craven, Kevin Williamson, Lawrence Kasdan, and many more. (Click here to read their testimonials.)
The benefits of using a screenwriting program are obvious -- it automatically formats your script so you don't have to worry about manually churning it out into the proper layout and the approved font. Lots of little features make writing much quicker and pain-free. It has plenty of bells and whistles, such as providing various templates, enabling you to include notes, allowing you to track changes between drafts, offering a "text to speech" function that allows you to hear your words read aloud, and much more. The new version includes a scene navigator and a page-count manager, among other nice new and/or improved functions.
So what's the bad side of screenwriting software? In a nutshell, no matter how great and fancy it is, it does not write the script for you. And even though it is an enormously valuable tool to help you finish your script, it does not guarantee that your story is good enough to be optioned into a production. Some writers invest so much money into software, screenwriting contests, seminars, script coverage services, and other tools (some of which can indeed be helpful), that they fail to realize that the bottom line is coming up with a good story, great characters, believable dialogue, and a well-written plot, which no software can really substitute.
Becoming a successful writer involves a mastery of creativity, sharp writing skills, industry connections, a knack for developing fresh takes on emerging trends, and a big heap of luck -- all combined in a holy grail that I and countless other aspiring screen-and-stage-writers have been pursuing for years.
Final Draft will not turn my story into a blockbuster movie, but it's a tool that helps me put my ideas on the page in a professional manner, and that is a big step in the right direction. The rest is up to me.