After the fiasco of losing all those words last week, I've been using Scrivener a lot more and I have to say, I've been finding it very useful. Here's a screen shot of one page -
As you can see, the central section is similar to any other word processor, but it's the features down the sides that I'm finding really useful for NaNoWriMo. On the left I had planned my chapters on little cards on the 'pinboard' (that appears up in the right hand top corner), but I've ended up adding extras as the story goes along because I'm useless at planning. Easy to do - just add an extra card in the right place and it slots in down the left hand side.
Then there's the other great feature down there on the bottom right - a place to remind myself of plot holes that I think of, but don't have time to go back and fix (there's a lot of those). I'm copying it all into Word, too, just for extra insurance, but I'm liking Scrivener more and more.
Now, on with the writing!