I love this plugin! It is so easy to set up and is very effective at stopping comment spam. It's much more effective than reCAPTCHA. Despite using reCAPTCHA, comment spam was totally out of control on one of my client's blogs. When I replaced reCAPTCHA with this plugin, it stopped comment spam completely. The difference is amazing.
I used to think I would have to get API keys from three different anti-spam services to use this plugin effectively, but that's not the case at all — it works just fine right out of the box! The API keys are completely optional, which makes setup a breeze.
Thanks for a great plugin!