I had to uninstall MT-Blacklist however (soon there will be a MT-3.11 plugin package that includes MTB). So far, my experiences with MTB have been pretty okay, though not overwhelmingly good. It deleted about 250 spam comment postings and forced moderation of about 35 comments (which were spam, mostly). The disadvantage of MTB’s approach is that fighting spam still consumes a considerable amount of time as it can’t fully prevent spam from being posted, just from being displayed. So I still had to watch out for new spam commments and manually delete them. I’d probably prefer approaches like those “real human” comment filters such as SCode or HumanVerify. I haven’t tested their effectiveness and efficiency yet however. And as a major drawback, these solutions aren’t very friendly in regard to web accessibility (visually handicapped people). The latter issue could eventually be solved by adding a dynamically generated sound sample of the displayed numbers.