Since the latest version (3.0) of Math Comment Spam Protection is now compatible with WordPress 3.0.1 and the Twenty Ten theme, I have switched back to using it several days ago. As is the case with any of these math protection plug-ins, it will at best stop some of the automated spambots. It will not prevent someone from answering the math question to post spam. 
Mark Headrick's Blog
My ramblings about what's new on my website and whatever else comes to mind.
