shutter blades
 

Does the number of shutter blades affect anything else besides the shape of the bokeh?

Rather actual shape of open iris. But yes.

Care to elaborate? What are the advantages or disadvantages to more or less blades?

In other words, I like the pentagon shape I get from the 5 blades on my canon FD 50mm 1.8, but am I sacraficing anything else like light fall off, sharpness, etc. I also have a 55mm 1.2 which has 8 blades I think. I don't notice any difference besides light loss but I don't have trained eyes.

http://en.wikipedia.org/wiki/Diaphragm_(optics)

just one more elaboration to this: All iris diafragms are designed to be virtually rounded in one posistion(in open). In other positions are corners between lamellas better seen.

Perhaps the biggest difference is bokeh quality in out of focus specular highlights. Some have suggested that hexagons are more distracting (and I would agree), than the rounder shapes produced by cinema type lenses. Given that edge diffraction from the blades should not be an issue below f16, I suspect the largest difference is just the bokeh thing for adapter purposes.

Actually cinema lenses produce quite polygonal specular highlights. One notable example is the shot of Denzel Washington in the car talking with Jodie Foster, in the movie "Inside Man." Specular highlights are clearly visible through the windshield of the car, and they're quite polygonal, in fact more so than what I've achieved with my Canon FD's.