Best used sparingly, I think. Jeremy Keith isn't really a fan from a usability perspective, and I can see why. He makes the point that this approach is better than using JavaScript to do it, on the grounds that (in theory) a user agent could allow the user to disable the autofocus behaviour if it's a problem for them.

I only used it here to save people who are adding a lot of docs from having to do lots and lots of clicking. They should just be able to type, hit enter, tab, enter, and then start typing the name of the next document.