I had considered one and two before, and strongly prefer one, but it hadn't occurred to me that people might operate by three. And I don't use the anti-kibitzer, mostly because I'm too lazy to get it working, and believe (probably erroneously) that I am not influenced by that. Also, I'd constantly be turning it on and off and then on again, so much so that it would only be frustrating.
I mostly use one, with occasional instances of two. For instance, I never downvoted the Popper troll from a few months ago, because every comment of eirs I saw was already at -20 and downvoting seemed pointless. My not upvoting Lukeprog is mostly two with a little bit of three. I used to use the anti-kibitzer, but it was preventing me from getting to know the other users, and long conversations with three people in them got confusing. I kept having to turn it on and off, and in the browser I had at the time that meant scrolling all the way to the top of the page and losing my place.
People who go back and downvote every post or comment a Less Wrong user has ever made, please, stop doing that. It's a clever way to pull information cascades in your direction but it is clearly an abuse of the content filtering system. It's also highly dishonorable. If you truly must use such tactics then downvoting a few of your enemy's top level posts is much less evil; your enemy loses the karma and takes the hint without your severely biasing the public perception of Less Wrong's discourse.
(I just lost over 200 karma in a few minutes and that'll probably continue for awhile. This happens to me every few weeks. Edit: I mean it's been happening every few weeks for a few months for a total of only three or four. Between 400 and 700 karma lost total I think? I don't mean to overstate the problem.)