I invested in Scrivener a couple of years ago. Because I also have a very long WIP which is in disarray by now with umpteen drafts and different scenes in different places. I'm not using it--I do think it would be extremely helpful, but I couldn't gather up the energy to sit there and actually learn it well enough for it to be useful. I think if you're willing to put in the time to learn it (they have all sorts of tutorials, but it would take many hours, portioned out over several days) it's a good thing. But my god I just couldn't face putting in the time.

Now that you've reminded me, maybe I'll try again over the holidays to master the thing.