I had been using the SI CAPTCHA Anti-Spam plug-in for wordpress to compensate for my DoS attack on my hosting provider issues. My hosting provider had implemented some sort of IP filtering and Akismet wouldn’t work at all, this caused hundreds of SPAM comments to show up in my pending instead of spam bucket and was taking me forever to sort through. I had installed SI CAPTCHA Anti-Spam to block the SPAM and it did work pretty well, it blocked 90% of the SPAM from getting through and combined with Akismet 99% of my SPAM never made it into my pending status.
However, I had to uninstall SI CAPTCHA Anti-Spam for the main reason that if a user forgot to enter the Captcha and clicked the submit comment button, they would get a 500 error and when they went back the entire comment they had typed would be erased and the reader would have to start from scratch. This hurt commenting badly and I had several readers and fans complain about losing their comment and vent their frustration at me.
In the meantime my Akismet is back so I don’t have to use the SI CAPTCHA Anti-Spam anymore, but I also get a little more SPAM in my pending then I did when I was using the plug-in.
Don’t implement something that will turn off your readers and commenters, this is a sure fire way to lose whatever regulars you have who comment on your blog.