my version simply saves evey vote in the db, including the time and what the user voted. this way, the db is used to check if you voted, so no ips.
also working on a vote history, where you can see who voted when (but not for what, that would be unfair
I'm actually pretty close to releasing a preview version, everything is working except for the limitations on who can post a poll.
The only issue left is (gulp) editing of a post/poll. Do you think it should be possible to edit the questions or not? (abuse here would be an issue)?