I didn't realize until today when Aryk pointed me to this article: iTunes Gift Cards now Canadapatible for purchasing apps in Great White North that the fact you couldn't purchase apps with iTunes credits was just restricted to Canada (or at least non-US)... I figured it was a limitation of the whole system. Turns out not, and that's good news, cause I still have $8 sitting from a gift card from years ago just itching to be used on the latest and greatest apps!