iscrollview bears no relationship to listview, other than one often finds oneself scrolling a listview.
iscrollview lets you scroll the content of an element within a page. The most common use cases is simply to have non-flakey fixed headers and footers. It will work with headers/footers either inline or fixed. Or using your own formatting for the header/footer.
Fixed headers/footers have gotten better since 1.2. But still have some flaky aspects. And they're really fake, because you're actually just scrolling the page underneath the header/footer. So, the scroll bar doesn't really make sense. Note how the scroll bar goes over the header/footer. With iscrollview you have a proper scrollbar that is the height of the scrolled window.
JQM official stance is that you should use overflow:scroll for this. Well, that looks nice in concept, but has only been supported in Mobile Safari since iOS 5, isn't widely supported otherwise, and doesn't quite work as one would like. For example, no rubber-band effect, so acts differently than the main page scroll. It's just too soon, needs to be more widely adopted, and issues worked-out.