3. Management. As I stated above, you can only really see one app at a time on the iPhone. With multitasking, you might have four or five apps running in the background--eating up battery life and impacting performance--and you may forget about them. The next generation iPhone OS needs to include some sort of interface or function that shows which apps are active so you can manage them properly.
4. Security. The iPhone OS closes the current app when you switch back to the main screen or accept an incoming call. This security model ensures that there are no apps running in the background and ensures that malicious apps can't be used to compromise the iPhone, steal data, or spread malware. As has been seen with jailbroken iPhones, enabling multitasking opens the platform to potential malware attacks.
While these are concerns, it is hard to ignore the fact that all competing smartphone platforms already include multitasking and that many focus on that capability as a competitive differentiator when comparing against the iPhone.
I am not suggesting that Apple's current pseudo-multitasking model is perfect, but I am pointing out that true multitasking is not without its issues, and that there are other potential solutions for a device like the iPhone which achieve the same results--or close enough at least--without introducing the concerns that come with multitasking.
Multitasking--true multitasking--is, in fact absent from the current iPhone OS. But, it seems like it is more of an issue from a marketing perspective than an actual concern of iPhone users. If, and when, Apple does introduce true multitasking in the iPhone OS, what will Apple competitors have to attack in their commercials?
The launch of the iPad changes the equation entirely as well. Because the iPad is built on the iPhone OS, and it has a significantly larger display to work with, users will expect to be able to open multiple apps and cascade or tile them to switch back and forth just as they are used to on desktop and notebook computers today.
While the value of multitasking on the iPhone itself may still be questionable, it would be a serious handicap to the iPad--even bigger than the inability to view Adobe Flash. Particularly when considering the potential business use of the iPad, multitasking becomes a critical element.
Multitasking is always at the top of the iPhone OS rumor list, though, so it may be premature to get too excited just yet.