Multitasking doesn't need to add complexity and stability issues, if ubuntu can do it then so can apple.<p>It does add more power consumption.<p>Multitasking is useful because humans are multitasking.<p>For instance, a navigator that guides someone to their destination could run in parallel to lots of other applications and be very useful that way.<p>Single tasking computers are pretty much done for, multi tasking is the norm, not the exception. By choosing for a single tasking environment a decision has been made that is going to be relatively hard to undo. All sorts of assumptions have now become embedded in places where they probably shouldn't be, such as dealing with screen input (focus).<p>I can see why though, it is possibly much harder to get a user interface up and running on a multi-touch display without a mouse if you have multiple applications active.