I almost never use farther. I think they're considered interchangeable for the most part these days. I always think of farther as an old-world sort of word and I'm not sure when you're even meant to use it. *shrug* Something to think about though.

The site I linked in the post seems to say much the same thing, so that's comforting. Every now and then I find I am so badly wrong in what I've been doing, but I had no idea.