This plugin is creating new users with no username.
I have tested it. The plugin sends out a confirmation email with the username and password to the person who registers, but in the administrator's list of users there is only a user ID number with no username.
If you try to log in to the site using the new username and password there is always an error, because the blog is unable to recognize the username.
There is another problem with the captcha. Even with the simple captcha, the plugin is never able to recognize whatever correct set of characters is entered. You can only get the plugin to allow new registrations if you disable the capthca entirely.
I have tested this over and over again and it is not working.
I am using WordPress 2.6.1
I hope there will be a fix for this bug.