It took me three watchings to figure out what they were trying to demonstrate. Between the colors (not to harp on the color blindness thing, but those color choices were dreadful) and the speed of the animation, its relatively difficult to even understand what is happening the first few times through.
I agree. The version here http://en.wikipedia.org/wiki/File_talk:Pi-unrolled.gif appears to move slower. I think it's better.
Anyone else thought that π(n) was referring to a graph of the density of prime numbers? :P