With iOS 4.3, Apple has enabled an experimental feature on the iPad called “Multitasking Gestures”. (This is only available if an iPad is being used for development, and even then it has to be turned on in Settings.) What these gestures allow you to do is quickly switch between applications from within them with four or five finger gestures. When using these gestures, you are able to skip the two-step process of exiting an app by going back to the home screen, then going back into an app by selecting it from the home screen. It is an attempt to alleviate this in-out-in functionality.
Guy English has some criticism for multitasking gestures:
These multitasking gestures add a set of interactions that relate not to what is on the screen but to an abstract higher-level of functionality. The touch screen is now an input into two systems: the application and the operating system.
The problem with this is the operating system is constantly presenting itself to you, even if this is more subtle on the iPad than on a PC. In almost every app, the toolbar still sits on top of the screen (as far as I can tell, games are the only exception to this), so the top-left always reads “iPad”. This is a constant reminder of the device you are using. Another operating system element that literally pops up on screen all the time is the keyboard. This is a function of the operating system available to all applications. As I type this in PlainText, operating system elements cover nearly half the screen. Even when playing a game or watching a video, the volume buttons on the side are used for adjusting the sound. The device doesn’t ever quite disappear when an application is running. Reserving a few gestures for operating system functions is not a bad thing, because you never use an app apart from the operating system, even if it almost seems that way at times on the iPad.
That being said, some multitasking gestures are better than others. The five-finger gesture (this technically still works with four-fingers) that takes you back to the home screen by pinching in is redundant. There is already a home button for that. Plus, this gesture can be inconsistent at times, because the system doesn’t know right away whether you are trying to press a button on screen, do this gesture, or some other gesture. The pinching motion is much more complicated than a swipe, so it may not be possible to fully alleviate this.
I find the simple four-finger swipes to be much more useful and less buggy. The system seems to know right away when I am doing one of these gestures. For example, the four-finger swipe up/down that accesses the multitasking bar always works smoothly. After doing this a few times, double-pressing the home button will feel incredibly cumbersome by comparison. It would be a shame to take these gestures away when two- and three-finger gestures are still available to developers. If an app needs a four-finger gesture to operate, that app probably needs to be redesigned anyway. In fact, these four-finger gestures do such a great job of mitigating the in-out-in functionality of iOS that I think they should be turned on by default.