I believe that the Planchon and Darboux algorithm is indeed what I am using. Is that what Wilbur uses too? The problem I think is that the fill basins algorithms seem to be better suited for filling minor pits in real elevation models, rather than fixing vast areas of bad hydrology in fractal heighmaps. So I get massive, very nearly flat areas that I have to fill in with some sort of noise and then fill the sinks again to get river systems that dont go in a straight line across the filled sink, or else designate them as giant, tens of kilometre big lakes. Neither of which is very good really.

I like that craftscape link, the erosion looks really nice. Not sure I really want to GPL my program just yet, though I suppose I could take a little peek at the source...

Thanks for coming back and giving me the benefit of your years of experience in this area!