Warning: Some-what off topic!
If I understand correctly it allows you to set your user visibility status with click, which I presume sets an existing attribute on the user table. that's cool, but what would really be handy is a generalization of this technique (at least to me!). Provide this functionality to set a user selected attribute (standard field names or any field in the table) and expose it on the interface, controlled by usergroup permissions.
It would be basically taking geo~oligists
Threadfields hack, AJAXing it, controlled by usergroups and forums, and then apply it to the thread, post and user tables, and for good measure it should provide hooks at key junctures.
The first thing I would use it for is to mark posts has to whether they have been reviewed by a moderator, even though they are technically un-moderated and exposed to the users before being reviewed.
Any takers? I think it would be a good candidate for a free/lite hack with a paid pro version! I'll order the first pro version!