Alright Apple, you win. You don't really want multitasking on the iPhone, and iOS4's halfhearted attempt proves it.
iOS4's multitasking is a mess of a feature. Yes, it lets you listen to Pandora while using other apps. Yes, it lets you freeze games that support multitasking, such as Plants vs. Zombies, while you take care of more important tasks. But in exchange for those perks, some of the iPhone's elegance is lost, and the advantages you'd gain from true multitasking aren't there either.
Let's be clear about what iOS4's multitasking is: Rather than run multiple apps at the same time, iOS4 freezes the ones that aren't in use, with the exception of certain functions. Music, for instance, can play in the background, VoIP apps can answer calls and GPS apps can give directions.
But most apps won't do anything except go to sleep, which means one of the classic tricks of multitasking, loading one task while you perform another, is not available unless the developer adds that function under a special task completion API. Some apps, such as Flickr, may take advantage of this feature for large file transfers, but others won't. Waiting for a YouTube video to buffer over a 3G connection? It won't go anywhere unless you're staring at the loading screen.
Then there's the issue I've seen acknowledged most often: Developers must add multitasking functionality themselves, and the majority have yet to do so. This will fix itself with time, but the lack of support dampens the initial impact of iOS4's marquee feature.
What bothers me the most, however, is the sloppy implementation of iPhone multitasking. Every time you open an app, it gets added to the tray, and the only way to close it is by pressing and holding any app icon, then clicking the top-left corner of the apps you want to close. If you don't micromanage, the tray quickly becomes overrun with clutter, making it hard to find the apps you really need.
When Apple chief executive Steve Jobs introduced iOS4, he said this: "When it comes to multitasking, if a user has to use a task manager, they (the developer) blew it." I suppose Jobs was referring to Windows Task Manager, which you use when all hell breaks loose on a PC. But taken literally, iOS4 has a task manager too, and all hell breaks lose if you don't use it. This time, Apple blew it.