If you read Roy's comments above, he says he is currently using 4 different plugins to combat comment spam. Ipstenu, you claim to be using 3 plugins. I have been using only one since September of 2007.
If I read Roy's comment correctly he suggested combining the approach used in Spam Free WordPress with Conditional Captcha, so I attempted to point out this would sour the effectiveness of Spam Free WordPress.
I utilized the link feature in replying the second time to encourage Roy to try the plugin, before making suggestions on how it should work without saying that explicitly.
Your comment about accepting other's choices and moving on was a bit harsh. I thought this forum was to help people, not funnel them into using only the three Automattic plugins mentioned twice on this page: Akismet, Cookies for Comments, and Bad Behavior, so now three times.
I do realize you (Ipstenu) mentioned refusing to use CAPTCHA, so my concept probably rubs you the wrong way. That is no reason to backhand me with a :).
To leave a comment on WordPress a human has to type in a username and a password. In the real world readers do not object to using only a password they can read while remaining anonymous, especially when it saves them from having to signup then sign in to an account on that blog just to leave a comment.
If it were true that having to type in a password would stop comments, no one would be using this WordPress forum.