Spam annoyed me so much that I signed up for Disqus comments. It seems promising and much more interactive.
I tried Intense Debate and Sez Who on my other blogs. To a non-pleasant outcome.
Intense Debate refused to install correctly on a blog freshly installed to the server, with no plugins.
Sez Who installed easily and it does keep the index on your blog, And even has a rating system. It just did not do anything for me. True I do not have a comment storm around here, but if people ever feel like commenting they have an option to add seesmic video. I also feel that the Disqus forums aren’t hurting the matter either.
I was going to try Haloscan on a blog with no traffic/comments, but I have not had the time to research and test it yet.

Thank Mashable for the convincing.