It’s nice that someone is working on an alternative to the Akismet anti-spam plugin monopoly.
With that being said, I saw a server load quadruple [from 4 to 16] in under 3 minutes after enabling the plugin on a friend’s site. It was right in the middle of being mercilessly hammered by spammers, but I don’t see how that should matter. Especially when their whole angle involves making a user’s browser solve a math problem.
Maybe they still have a little more work to do.