I've implemented support for this in my tree, but I'm holding off to commit until APR accepts my patch. This is so nobody else goes to the effort to implement this when I already have :)
What this means is you'll be able to do: <farm> <name>FooFarm</name> <usefarmer count="5">Farmer Bill</usefarmer> </farm> and it'll run five "Farmer Bill" farmers in parallel. -aaron
