Just a quick post. Pretty much my favourite plugin here has been Commentluv by Andy Bailey. Unfortunately, enabling IntenseDebate meant that Commentluv stopped working. However, our favourite programmer/purveyor of fine food has written a Commentluv plugin for IntenseDebate. Cool, eh?
So we get threaded comments, single sign and Commentluv all in one place. If you wish to take advantage, there is an extra field under the comment box for you to put in your site URL.