Here is a link to a very good example of a well thought out ScrollView API and some examples of what can be built from the API.
Edit: ATM most of the GUI solutions for Unity is too focused on desktop. Desktop GUI design paradigm is very different from Mobile. For example, on mobile, due to screen size, a new paradigm of user interaction was created to overcome the limitation. Flicking and panning to view more content, pinching, etc. Technically, at the very heart of this new paradigm is the ScrollView component. As can be seen from the example link, many types of user interactions are possible with the ScrollView component as the foundation.
A more robust ScrollView component in NGUI would enable Unity developers to be able to create Mobile user experiences that are more in line with what user of IOS and Android are accustomed to and will come to expect.
Examples :
http://code4app.net/category/scrollview/1Scrollview API:
https://developer.apple.com/library/ios/documentation/uikit/reference/uiscrollview_class/Reference/UIScrollView.html