Well, chalk up another one to new experiences--I voted at the local voting station with no problems. My name was on the list (albeit on a seperate sheet, marked,"foreigner"), and I signed it after showing my ID and voter registration sheet, and proceded to vote.
There were six ballots, and the only major surprise was that two ofthe ballots were for "proportional representation," one at the municipal level and another at the provincial level. I'm not sure what that means exactly, but on those ballots, we were required to vote for a party rather than an individual.
One of my friends said that there may be some deviation in practice from the published wording of the eligibility regulations. Apparently all foreigners with an F-5 visa were given voting information and voter's registration numbers. Perhaps the three year requirement is applied to total residency, or to the residency in Korea after receiving the F-2 visa.
I'd like to encourage all other permanent residents to get out there and vote, if only to affirm that you value the privilege.
If voting rights aren't enough for you, check out my fellow Sokcho blogger Gangwon Brian's interview with two people who have decided to become Korean citizens. Interviews are here and here.