cool. I thought I had read in an issue of Popular Science or Discover magazine that one blade was theoretically the best but I don't know enough about it to say for sure.
I'm not an expert but I'm pretty sure there is a big difference from a device trying to pull energy out of the fluid.
A quick google didn't lead me to an authoritative source, but I know I have read many times that a one-bladed propeller is the most efficient.