An effective, low-cost add-on with great XenForo implementation. Didn’t test the older versions, but it seems most of the past complaints about this plugin have been addressed. Very easy to install and deploy. While it has let some spam user registrations through, it thus far has been blocking their posts. Quite happy with it, and I can sleep more soundly now (literally). This is an anti-spam solution that I would love to see integrated into XenForo mainline - it just works™.