Connectivity
I have degrees in market research, so for me one of the coolest things about making games for the iPhone is that, whether through 3GS or Wi-Fi, you are always connected to your players and can get all kinds of feedback from them. All our games have feedback/comment buttons so our players can give us feedback and thoughts on our games. We listen very carefully to what they say. Feedback has been a fantastic development tool to for us.
Another great thing about connectivity is the amount of analytic data you can collect about your players and games. Whether you're using your own stats package or one of the many packages available to the developer (Motally, Mobclix, etc.), you can look at all kinds of stats immediately and you can learn and tweak to your heart's content. You'll find average game times, average session times, specific events within your game, favorite levels, etc. If you are tuned into this stuff, it can help you to make big improvements in your games in just a short time.
Whether you are listening to feedback, paying attention to your analytics, or both, the ability to be in constant contact with your customers allows you to develop iteratively and can give your games a very long tail.

Mon, 01/11/2010 - 11:04
Maybe I'm jumping the gun here, and you'll be getting around to this soon. But I think the coolest thing about getting user feedback and stats from your software is being able to update the game to make an even better user experience after release of the game. This isn't selective to the App Store and mobile markets either, most of the console games out there are now patching their games after releases and adding new download-able content. It's not just about learning about things you did wrong and making sure it doesn't happen again, you can fix it right away and shoot for the best user experience possible.