It's better than nothing, but as mentioned before, I'd prefer something that systematically eliminates the downvotes rather than upvoting over them:

Let's say I've made 1600 comments, received +2400 "legitimate" upvotes, and -400 "legitimate" downvotes.

Thus, I should have a karma of 2000 (86% positive). But along comes Eugine, and downvotes everything, giving me another -1600. This puts my karma at 400 (55% positive). You then run a script to upvote everything he downvoted, giving me +1600 karma. This puts me at 2000 (66% positive).

As you can see, I'm STILL below the 70% positive that Eliezer mentioned as his intuitive threshold for "quality contributors", even though in reality I should be well above that threshold.

This is, in fact, what pissed me off about my karmassassination in the first place - my 'fake internet points' don't matter to me, but my ratio of upvotes to downvotes DOES, because I use it to track how likely it is that I have systematic flaws in my reasoning. This breaks down when the majority of my up- and down-voting comes from one or two concentrated sources, even if one of those sources is directly countering the other.