That's an interesting discussion and article. I sort of do this already for new features. You really feel the power of it, when after writing a lot of stuff you realise that there's a hitch, rewrite from earlier and shudder at the thought of the mess and wasted time if code had been written. In its final state the document becomes a series of steps that I can check off, which is helpful in a motivational sense.

I had thought of involving users in the design of new features via the support forum but I'm afraid of how that might turn out. A readme type document would probably be about as good a way of doing it as any though.