I use Bad Behavior as my only anti-spam solution. For my own reasons, I don't feel completely comfortable with Akismet or Spam Karma 2.
I've been receiving a ton of manual spam comments since upgrading to WordPress 2.0 (confirmed as manually submitted by ioerror, author of Bad Behavior), all of which are slipping past Bad Behavior.
I noticed that almost all of these spam comments have an all-numeric user name. So I cooked up non-numeric-names, which simply marks as spam any comment with an all numeric name.
It's not a fool proof anti-spam solution, but for those of you (like me) with qualms about some of the other tools, this might help minimize the amount of moderation you perform on a daily basis.