Definately go USB or even keyboard port for a mass market encoder. However I'm not totally opposed to using a parallel port hack for my home use. Do you happen to have any links to any other parallel port dart board hacks?
Most the information on the havard guys site is no longer around (hence why I'm linking to a web archive version of the page). But I thought was relevent information and might help us to figure out this hack, or give RandyT more information to help his endeavors. I did email the guys that were involved in this project to see if they can forward me the missing pictures and files from their page. I promised I'ld get it back up on the web to share with everyone else. Maybe get the page hosted up here at BYOAC. I'll let you know what I hear from them.