I subscribe to the comment feed for my blog just to see what comes through, and when I spot any spam I come over here and delete it. That doesn’t happen very often, because WordPress’ spam catcher does a great job. The amount of suspected spam comments has increased slowly, but just now there were 123 suspected spam comments, almost all porno type things. The spam catcher stops this truly heinous stuff, but I’m going to keep a close eye on this and if it seems like too much stuff is slipping through, I’m going to change the settings so comments are moderated a bit more before they’re posted.
So, consider yourself warned. I don’t want to have to ask people to register, so I think the next step will be only allowing comments to post immediately if the commenter has a previously-approved comment (though there does not appear to be a way to build this list before turning on the feature, which is unfortunate).