He had grown tired of doing it by hand and implemented a automatic Baskervillification of all ampersands into the function.php and style.css. Excellent idea, I implemented mr Withcrofts tweak myself. Not that Minion Pro’s ampersand is that different, but Baskerville is a bit nicer and this tweak forces the italic version to show up everywhere.
His tweak was really simple to follow and usable for any WordPress-site that doesn’t use Baskerville italic for bread.
(Update: Xponent.se has been redesigned since this post and the tweak is no longer active on the website)