The reason why people like to use the iPhone so much at first is that it’s intuitive. Intuitiveness is always something that impresses you in an interface, because it doesn’t take additional knowledge to work the device. Simplicity is not necessarily intuitive — just see any Web 2.0 app with a blown up kids interface or the new Nano.
I’d be willing to say iOS has the best interface on Earth right now… but just look at Microsoft Word 2003 to see what happens when you start adding feature after feature to an interface that used to exude elegance.
