Graphic word verification blocks spam-bots

Blogger has a graphic word verification feature which prevents anyone from commenting on Blogger blogs (assuming you have the feature enabled) unless they can read a distorted graphic image of a made-up word and correctly type it in. I've found that it works extremely well. No more spam, unless somebody types it in by hand.

Has anybody had any experience with graphic word verification in Blogger (or elsewhere) where spam-bots seem to be able to get by it?

-- Jack Krupansky