The facebook iPhone application is by far the best designed iPhone web app I have seen to-date. The functionality of it mimics a native iPhone application and is just as smooth on a wifi connection. On an EDGE connection, there is a noticeable preload (naturally due to the connection) but facebook preloads it using AJAX and renders the content only once it completely loads. This touch makes the application native. The user doesn’t get frustrated because there is still some content on the page, not just a plain white screen.
It’s pretty silly looking in a browser, but on an iPhone it’s remarkable.
Keep up the good work.