Expanding some thoughts behind this tweet:
Ever since the iPhone got the App Store, I’ve had this feeling that the hardware has some magic about it - that it can transform into anything, that the screen is like a pond, a magic mirror that can turn the device into something completely different for every app or use.
The lack of (third party app) multitasking on the iPhone has been a major gripe for reviewers and customers since the device came out, and both the Palm Pre and Android phones support as much multitasking as you like. Apple’s official stance is that it would drain battery life too fast, but I think there’s more to it, and that it’s one of the crucial design decisions that make the iPhone a great device. From this decision follows radical simplicity in key areas.
It really comes down to controls and simplicity. If you have multitasking in place, you need to put controls on the device, or use parts of the multitouch screen for controls that manage the multitasking. On the Palm Pre you flick between app “cards”, for example. I’m not sure how the Pre manages this exactly, but some gestures will in such a setup always be reserved for the operating system to handle this multitasking, and presenting a UI to the user for this.
I think the reason that TomTom, Zipcar and a ton of other app makers are on the iPhone platform and using the device as a blank slate for their purposes is that they get the whole thing to play with. The whole screen and functionality of the device (yes yes, with some exceptions) is given over to you once the user starts your app. No gestures are reserved for switching apps, no menu will cover what you put on the screen. It’s all yours, once the user has given you the go by launching your app, and asked you to transform their iphone into a car key, a GPS device, a camera, a todo list application or a koi pond.
This is key - the operating system gets the hell out of the way, because it doesn’t need to be anywhere on the screen. On a device that is in many ways too small and powerless to do multitasking well, the iPhone OS just gives center stage to the current app and gets out of the way, letting the apps transform the iPhone into just what you need for performing the task or entertainment at hand. The best apps are the ones that use this paradigm to the fullest - they do one thing, with a super polished experience.
There is a single button for the user to press when she wants to switch tasks - the home button that kills the current app. In a way it’s the only button on the device - the sleep button, volume buttons and ringer switch are all added later as things that did need hardware buttons to be convenient. The whole OS is designed around the idea of a single button, and that’s quite a design feat in my eyes - having a single button that frees up the big touch screen to be anything. I think this is where the magic comes from - for both users and app developers.
Of course there are a number of cases where the lack of multitasking becomes pretty stupid. But how would you design the multitasking interface with a single button and the same power to the current app? We could all probably think of something clever that would work for power users, (like the Pre has, clever but not intuitive at all) but really, something that is as clean and simple as the one app at a time paradigm, and one button to rule them all?
I don’t think the multitasking restrictions will change anytime soon, even when the hardware becomes powerful enough to handle some amount of it, because it’s at the core of the iPhone OS and iPhone/iPod touch hardware design. There will be a point when multitasking on an Apple device becomes possible and relevant, but I think it will happen on a new product line or much re-designed hardware, not on the iPhone or iPod touch as we know them today.