Since iOS apps are now worth a billion dollars, here’s a few design notes worth bearing in mind when writing your new app:

• Users love receiving push notifications, and love it when you take them to the appropriate page in your app, but they hate it if they see the notification there. Make sure that the page you show contains stale information and does not automatically update to show the notification they just tapped on.
• Increase the number of times users open your app by keeping them in a continual state of confusion as to whether they have any unread notifications. At no time should the notifications shown in the iOS Notification tray, the number of notifications shown in the app icon badge, the number of notifications in your app’s own button badge for notifications, or indeed the list of notifications in your app match.
• For additional bonus confusion, none of the above should match the set or number of notifications the user would see if they opened the notification list on a computer.
• Users love pulling down to refresh. Even if your app is only ever used in a “read new things” kind of mode, always force the user to pull down to refresh, never update for them.
• Your app is only ever going to be used online, on a super-fast internet connection. Never cache data between invocations. Always clear the screen when loading the new data, users love seeing a spinner and a “Loading” message when on a slow connection.
• If you build your app around WebView you may be forced to accept that there will be some caching, fight against it and avoid a consistent experience at all costs by never saving this cache between invocations. Since it’s almost random whether your app will remain in memory between uses, this means it will be almost random whether your user sees stale cached data (which you don’t auto-refresh, obviously) or a white loading screen while you pull all new data.
• Tap targets should be as small as possible, testing in the Simulator with your mouse proves that Apple’s 44px guideline is way too large!
• The app should regularly reflow its content so that tap targets move under the user’s finger between the time they start their finger moving and the time it reaches the screen.
• Using a WebView for your app is great, the lack of JIT and other performance improvements means you don’t need too many servers to serve content to your app. Users love it when shared photos show up as black boxes because the servers are too busy.
• Using a WebView also means you can continually adjust the layout of your page. For the ultimate rapid deployment, never cache resources such as CSS or images client-side. Users love that retro look and feel when your page renders without them on a slow connection.
• Your app probably has to let users post content too. Users are always on fast, reliable data networks. Don’t worry about handling error cases, timeouts, etc. it’s ok to just throw an error, and ideally throw away their post too. Never double-check whether the post succeeded, for that to happen and the response being lost is impossible.
• Whenever Apple release a new API feature, make sure you update your code to take advantage of it. Apple’s documentation can be kinda waffly though, don’t bother reading all of it, you never need to handle the edge cases like someone taking a phone call on their phone (who does that?) or receiving a notification while you’re dragging your neat side bar out. Users love it when that side bar sticks half way, it’s hilarious.

For a perfect score on all of the above tips, I highly recommend taking a look at Facebook’s iPhone app.