I tried a few different anti spam, but they just move the comments to the spam folder. This one blocks them completely so no work for me. Real visitors can still comment.
This plugin is also the first plugin I have felt the urge to donate to, so I sent the author a small amount. I urge you to do the same if you find this plugin saves you from spam like it did for me. My time is valuable and each minute I spend going through spam comments is a minute I could have spent building my business. When I'm wealthy (next year?) I'll send more :)