In addition to KeyCaptcha we are also now using the Registration Form Timer add-on by Chris Deeming. Combined it means if somebody is actually able to fill in & all of the text boxes and complete the KeyCaptcha puzzle within X seconds then they are blocked but if they get past the timer check they are still then bumped up against StopBotters. The end effect is that the bots should be getting caught by the timer check & KeyCaptcha while humans should be getting caught by StopBotters. So far it showing to be a very effective combination.
Looking through the logs, this one caught my attention.
They spent nearly 10 minutes on the registration, either because an automated script got hung up with the puzzle captcha or a human couldn't figure out the puzzle, and then end up getting blocked anyway. That, that amuses.