Generally, I like it very much.
I mind the dollar sign as well. You could make it say "Total" instead or just have the numbers there... What about making the size exactly so that the URL-field vanishes? Some webapps for the iPhone/iPod touch manage to do just that... (It's still there, really, just moved away...)
I'd make the buttons a tad bigger with more spacing.
Oh and, yeah: It's another way to explain to me why web-apps are a bad idea. I create my shopping list on this, leave the house, and when I'm at the supermarket, I notice that there _is_ no free WiFi there, which means that my iPod touch tries to reload the page (for some or other reason) and my shopping list vanishes. Blech. I'm soooooooooooooooo looking forward to Apple's SDK, and I sure hope that it'll be possible to create such list-apps as a simple user for yourself, without having to go through some complicated (and expensive) signing process, having to download (your own apps even!) through the iTunes Store...