Some of the apps that are coming out for mixing boards and DJ scratching — they all look really cool, but they suck to use. You can’t physically turn a knob on the iPad screen — so why make knobs an essential part of your interface?
Finally, give users what they want — and a little more. In addition to enabling users to use your service effectively and efficiently, make them also think, “Wow, this application is genius.” Exceed their expectations desirably. If you do so, they will use your website or app not because they have to but because they want to.
There’s some discussion on Apple-centric and tech news websites about a video that’s doing the rounds with a new approach to notifications for iOS. While the system in the video is really nothing new (there’s been at least one alternative notification system in the App-Store-for-jailbroken-phones “Cydia” since 2010) it is getting a lot of attention, presumably because iOS users are quite satisfied with almost all the interactions of the OS except those dang stacking modal dialogs that interrupt your game of Angry Birds every time you get a text message.