WordPress seems to be returning 304 Not Modified for my feeds even when it should be sending the content. Weird.
It seems to have something to do with not having posted for several days. It’s not really WordPress bug 1275, since after creating this post the feeds work again, but that’s the closest I’ve found so far. (And by the way, requiring cookies just to do searches sucks.)
I’m the anonymousbugger who entered WordPress bug 1323.
…which is now fixed. Thanks dougal!