Thanks Gizmo for the plugin, it's been great.
We've had it installed for a few months and have reported 13 so far. Very few spammer have gotten through, and when they do they have already been reported by others.
If I had a wishlist it would be having the ability to audit all registered users against the database, as I know we have a ton that snuck through before the plugin. I think the daily API limit is 20k queries, so you'd have to have the ability to break it up into chunks.