Now that I’ve tested WordPress 2.1 and found that the themes and plugins I use work fine (there was a slight problem with PHPEnkoder, but it turns out that problem existed before and I just hadn’t noticed it; the author has since squashed the bug), I upgraded all the sites to run the new version.
Of course, they also released another new version in the last couple days, which Dreamhost will soon have available for updating. Oh well, at least that one will be slightly less worrysome since it’s a minor upgrade.