How about this? Apple could have allowed the user to choose any four apps that would have background access at any one time. They could have even included a simple multitasking slider control, to allow the user to choose between greater battery life at one side to greater performance on the other. Nice and simple, and a great compromise so the user doesn't end up having to quit applications like they do on Android.
You see? I thought of that in five minutes, and I'm not as smart as Apple's engineers. What I saw today was a half-measure. My proposal gives the user true multitasking, without a confusing interface.
As for notifications, the Palm PRE (sales notwithstanding) has a superior notification interface to the iPhone, and allows multiple information to appear the screen at the same time. In addition, it's done without Apple's current dialogs which bring whatever you're doing to a halt so you can dismiss whatever SMS, FaceBook, or similar notification is in your way.
Trying to think of ways to improve the iPhone isn't trolling. Maybe you just haven't spent the time thinking about it that I have.