I actually find the iTunes store on the iPhone to be quite terrible as well.

It takes longer than any other app to power up and then greets you with a "Loading..." routine. In case you get over this it will do it again every time you switch to a different item on the menu, e.g. Search. It's like it's not sure of itself and must phone home before displaying the UI to, I don't know, show a user the "Purchased" screen. Same deal with the App Store and Mail apps. All very clunky.