David - I noticed you've mentioned transparent surfaces and seem to have them included in a couple of screenshots, along with (unless i remember incorrectly) shadow volumes. How do you get the two to play nice with each other? Do you shadow the transparent polys or just draw them without lighting?
I've got a similar system working ( http://studenti.lboro.ac.uk/~cojc5/Vecript/SoftShadows.png
) that uses a similar method to shadow volumes, but i've yet to add transparent surfaces. At the moment if i do a pass per light then the transparent surfaces are going to end up being drawn waaaay too many times
At the moment the only solution i can think of is to draw them at a reduced alpha value depending on the number of rendering passes they'll be included in..