Mollom Just Gave Me An Hour A Day Back
centernetworks.com
centernetworks.com
As the author says - a CAPTCHA solution reduces comments significantly, lets say by 50%. So if Mollom marks 10% as spam, and half of those are actually legit, 2.5% of comments are lost.
But that's not a bad price to pay for getting an hour of your life back a day.
I'm using Akismet on my blog, and comments considered spam are held in limbo where I can approve or delete them. No comments should be lost unless I accidentally misjudge a flagged comment.