It's an interesting way of breaking thing down and still keeping track of them.
There's a free tool available from http://freemind.sourceforge.net and some examples at http://www.mind-mapping.co.uk/mind-maps-examples.htm. And it's proving very useful for tackling some big problems I'm having with respect to organizing what I know about a BIG system. The only limitations I deplore are a lack of Undo and an inability to connect one leaf or branch to another leaf or branch, though the latter, I understand, is a much, much harder problem than the original one this simple tool tackles.
And, yes, it's proven very useful for the first several stage of a snowflake approach to my thinking about a novel. Don't have a clue where that's going, but it's been fun just noodling with it and trying to answer my own questions.