I've used this for over a year on a large forum with over 20 million posts. It's been working with no problems. We get a LOT of spam signups and this is pretty helpful to get rid of them. Configuration is complicated, and it does reject some users who I later choose to accept, but it works.
Absolutely essential tool for preventing targeted spam from VPN users, mechanical turk farms, etc. 2.x has been missing this and Xon delivered. Importing our old settings from TPU Detect Spam saved a lot of time.
If configured correctly, completely stops spam and banned users from coming back and trying to cause havoc. With the GetIPIntel integration added in 1.6.0, it does a great job at detecting proxies/vpns and "bad ips".
This add-on has greatly reduced the amount of spam we get over @ our site. Prior to installing this, multiple spam accounts per week would slip through and be allowed to post spam threads. 99% of them are caught by the advanced filtering rules in this mod.
Highly recommended for any website suffering from a spam problem
This is most likely my favorite add-on developer. Signup Abuse and Protection, User Essentials, and Conversation Essentials are all must haves for your forum site. Furthermore the dedication and hard work Xon has shown in keeping his add-ons up to date and bug free are tremendous. All three add-ons are well worth the price.
Absolute essential add-on to reduce tedious moderator work and cleanup. Extensive set of options let you tweak rejection logic to suit your site making this add-on a no-brainer. Have been using for a few weeks now and can't imagine going without it for future projects.
Xon's take on this addon has been a blessing for our site. It helps track Alts, stop VPN abuse and so, so much more. We had a problematic user who after a long tale involving months and 80+ alternate accounts and several VPNs, finally got put in their place and prevented from returning to the site with this addon. Every attempt for this malicious individual to return has been stopped in its tracks since then. I won't also forget the rest of the more normal ban evaders and the such.