I did it. As considered about a year ago, I started my distance learning studies in screenwriting. I've gone through the first few lessons and tests and am very satisfied so far. I haven't learned that much brand-new stuff, because right now it's all about plot, characters and conflict - things you need in novels, too ;-). So the exercises aren't only helpful for screenwriting and it will get more specific soon.
The fun thing is, I already see and watch movies through different eyes. As in: Why is this scene necessary? Could it have been left out? Why am I not relating to this character? Why is this a tad boring - no conflict potential, no identifiable characters, or is the setting unbelievable?
I've been niggling like that when reading books for a long time, but now my sense for questioning every element of a story has sharpened. Like I said, the lessons so far don't only apply to screenwriting, but to any writing. Especially my own.