Was it multitouch screen? The integration of multitouch + the web was pretty amazing and I would consider it a killer app over the arrow based web browsing that

Was it multitouch screen? The integration of multitouch + the web was pretty amazing and I would consider it a killer app over the arrow based web browsing that came before the iPhone. Full web + multitouch(zooming and selection of links are amazing) + high DPI screen + large enough to get things done without being too big to fit in a pocket == killer app. When I say that there wasn't a competitor that was close I mean in total experience not just having the web. In my opinion all the little things matter immensely.