The ConfirmEdit extension page states "Unfortunately, as of 2011, some spammers appear to have figured out a way to bypass it, either through character recognition or by using humans. For that reason, it is not necessarily recommended." in the recaptcha section.
We've implemented QuestyCaptcha with questions that should be easy enough for most people and waste the time of spammers if they're desperate to spam.
With the exception of one question all the answers are on the wiki main page.