Personally, I find script format to be extremely limiting in its 
storytelling ability.

It depends.

Certainly does.  I used to write scenes for my improv theatre group.
Little playlets, dialogue, minimal stage directions, script format.

Thus, when I started to write fanfic, I tried script.  It didn't
work. I've no idea why, really.  I've written stories in script.  
But my style of fanfic (loads o' angst) seems to require prose, if
only for the inner monologue.

Take a look at Atonement, the excellent tho' disturbing fic posted
recently.  I can't begin to imagine this in prose.  It would be
wrong.

So it depends on the story, the author, the mood...

--Sean Gaffney
--"But Sean, this doesn't say anything!"
--"Oh, thank you, Minister."