If you're writing for the entertainment industry for a living or just trying to write your first screenplay, you need the right software, and that's Final Draft. If you're trying to get your foot in the door or get your script taken seriously then you really need to make sure that it's in FDR - Final Draft Document format (or .FDX if you happen to be using version 8 of the software).
The software is renowned in the entertainment field for its user-friendliness and for the fact that it saves you a lot of time when writing. Final Draft formats everything correctly automatically so that you don't need to worry about the correct format for a script. All you need to do is make sure that you're writing something that people will want to see and you're set.
It's a real challenge to get a screenplay produced, and as crazy as it sounds, even a great script can be rejected because it's formatted poorly and the script-reader refuses to give it a chance. You need to make sure that your screenplay, TV or audio script is in the correct format before submitting it anywhere, and Final Draft is the best way to be sure of it.