I just started, though I don't know why I waited so long. It's so much better for me than a notepad or document where I end up revising over and over just to get the ideas down and structured. I'm finding I can get the same thing done with a map in a quarter of the time.
I'm using
Freemind, which avoids the running off the edge of the paper problem. The ability to move entire sections from one node to another are a must for me. I don't think I could do it on paper. I'd need a wall and a bunch of stickies or something.