Push notifications are something that App Developers and iPhone fans have been waiting since long. Originally it was expected that the firmware version 2.2.1 from apple would enable Push Notifications.
Background tasks cannot be run currently on the iPhone making IM applications useless unless they are kept open all the time. The same holds true for the recently released Skype app aswell. However, putting all the delays behind them Apple has now announced the availability of push notifications for developers to begin testing.
Apple is surely working over time to prepare its next-gen iPhone firmware and AppStore to compete with upcoming Palm PRE, Nokia N97, HTC Magic along with new App Stores by Nokia, WM, Samsung, Acer, Blackberry etc.