I don't vote down often. I do vote up, including sometimes for good arguments by people I disagree with. I try not to just vote up for agreement, but well written points of view. Also vote up for wit or just plain funniness.
Occasionally I do repair work, voting up someone who has been blasted for no discernible cause. Sometimes thumbers chase people around apparently in some kind of retribution. I'm mixed about doing that type of repair - pro, re showing general respect for the poster, and con, re letting the nincompoopish down thumbers be seen.