While I guess that filling in the wrong arrow is less likely to happen than some other systems (ala the "butterfly ballot" for punch-cards), this was a major pain in the ass because the little voting booth-ettes are still the same size and style that was used for the punch cards, and this poster that they handed us just plain didn't fit!
They were saying that if you used the "special pen" all you'd need to do was a simple line connecting the arrow's back and front, but being the obsessive-compulsive guy I am, I had to fill in nice thick black lines the same size as the arrow on the page.
I wonder how many people will bitch about the size of the card, though ... I'm a big guy and I found it unweildy, I can only imagine what "a little old lady" 1/3rd my size would have to do to deal with it in those voting booths!
What was really a pain in the ass was the second side with a bazillion "judicial retentions" to vote on. Of course, I always go through an vote "no" just on Discordian principle to all of these, figuring that if the judges aren't dickheads they'll be getting plenty of "yes" votes, but I want to help throw out the asswipes ... but that was a hell of a lot of scribbling.