The tool works well, but without the captcha it's spam heaven. Unfortunately the developer chose a captcha that the author says "never use this in production, it was an experiment!" it's unfortunately way too easy to read so spam registrations flow in freely anyway. It's also not accessible to the blind (visual only). I suggested using recaptcha from carnegie melon but the author never responded to comments on his blog or via email. Too bad, the simplicity was perfect but I couldn't deal with the spam registrations.
===> one star