If you are developing a content-based iPhone or iPad app that connects to the internet you have to be prepared for real-world networking. The fast hard-wired connection you have on your development machine and the strong wi-fi signal you get on your device are great for testing things quickly, but they don't prepare your app for what it will face in the hands of iPhone users all over the world. Your app will have to handle network dropouts, packet loss and high ping times without crashing and while maintaining a good user experience.
Last night DesignHammer hosted the Coder Lounge for Triangle area Drupalers. A small group of us worked on porting several Drupal 6 modules to Drupal 7.
I've learned a lot as a developer over the years. As time goes on, I learn new techniques that help me to write better code more efficiently. One of the big steps along that journey occurred when I learned how and why to use version control.