In iOS 5, a list of notifications can be viewed from within any app by swiping down from the top of the screen. This makes the swipe-down-from-the-top-of-the-screen gesture a system-wide gesture.
I agree with Guy English that system-wide gestures are not desirable: the beauty of the iPhone/iPad is that it becomes the app that is running. Having system-wide gestures means that those gestures are not available to the app that is running (or the app needs to have preference settings to determine if the app or the system will respond to those gestures, and that is not desirable either).
For example, if I am playing a game like Fruit Ninja or Cut the Rope, I might want my swipe-down to cut a fruit or a rope, not bring down the list of notifications.
I believe the solution is to bring up the notification list when the user double-presses the home button. Currently this brings up the app-switcher, but if you notice, the app-switcher is just a row of icons at the bottom of the screen:
The space above it shows the springboard or the app that was running. But showing that is of no use. We consciously double-pressed the home-button in order to pause what we were doing and do something else.
I think that wasted space can be put to great use by showing the notification-list in that space when the home button is double-pressed. The notification-list and the app-switcher can be animated onto the screen from different directions and with different speeds so that the users are aware that there are two separate entities being shown.
This alternate approach won't interfere with the gestures available to the app and it won't be copying Android!