Before I experiment with the many other options, I thought I'd ask what people recommend.
Hi Dan,
I don't have any experience with MediaWiki antispam solutions but with Drupal I use http://drupal.org/project/spamicide: "Spamicide adds an input field to each form then hides it with css, when spam bots fill in the field the form is discarded."
That's not only much more userfriendly as it doesn't require any extra effort from the user but quite effectiv for preventing spam. I shouldn't be to difficult to use the same mechanism in an extension.
hth Frank