Ok, so we can agree that the iPhone needs multi-tasking. It uses "saved state" (when you open an app it goes back to where it was) and notifications to fake multitasking, which works great on many things, but others like Pandora or a SIP app it can't quite pull it off. This is bad.

On Android, it is the opposite. When you press the home button, the app remains open. Pandora, SIP clients, and others work great! However, most apps must be manually killed from an App like TaskKiller. Most apps don't have a quit button, so they just keep running, taking up processing power and wasting battery. This is bad.

This is how it should work :

A combination of these approaches would work best. In Android, when an app is installed, it must declare certain needs, such as Internet access, GPS access, etc. Multitasking should be added to this list.

All apps would default to being a "saved state" (like with the iPhone).

If an app though it could use multitasking (SIP, Pandora) it would explicitly declare this. If the app requested multitasking it would be required to implement a "quit" button that would kill the process.

This would allow the iPhone like system of saving processing power and battery but introduce the multitasking goodness of Android, without the complications of an app like TaskKiller.