My polling web part now supports allowing for only 1 response per user. Thanks to Jason Mitchell (elektronisch) for providing the enhancement!
When you respond to a poll, a cookie is saved that keeps record of your response to that particular question. Also, the "Show Question" link has been removed because you can't respond again so there's no point in going back to the form.
Also, after you've replied to the question and you come back to the site at a later date, rather than seeing the question again, you're presented with the results automatically.
Thanks again to Jason for this enhancement – and for others who've downloaded my source, let me know if you have made any other neat enhancements that we could publish (I'll certainly give credit where it's due).
Check out Version 1.2 on codeplex to download this latest release of my web part.
Phil