Hi Peter,
I've been hoping your plugin would solve the problem I've had with a few persistent registration spammers. After I installed and configured it yesterday, I was disappointed this morning when I saw that one of my usual registration spammers had once again re-registered himself despite the plugin.
I logged out of my blog and tested the registration function, and I found that it registered me and emailed me a password even when I left the "Anti-spam word" field blank!
What gives?