From a technical perspective, multitasking in iOS4 is markedly different than what is featured in Android. As with many technologies adopted by Apple, multitasking in iOS4 has been implemented with a very specific user experience in mind.

Android lets the entire app continue to run in the background. A good example is the Nintendo emuators by Youngh. If you use one of these apps then switch to something else, it'll keep running in the background, sound and all, until you decide to close it or your phone runs out of memory.

On the other hand, iOS4 lets apps keep certain features running in the background (but not full apps; for example, you'll be able continue a Skype call or keep listening to your Pandora station while using another app, but the full app isn't running), have its state saved (as with previous versions of the iPhone OS), both, or neither, as desired. In this sense it could be argued that the iPhone OS has always supported multi-tasking via state-saving, and this most recent addition is simply one more tool for developers used to tweak how their app is experienced.

To you, the user, this appears as a list of running applications, both "backgrounded" and "paused." Now iOS users are free to stream internet radio, chat, and browse GeekTech, all at the same time, regardless of how detrimental it may be to battery life.

As for comparisons between the multitasking implementations on Android OS and iOS4; The two are subtly, but fundamentally different. With Android, the operating system itself controls much of the multitasking, while iOS4 allows developers to choose how their app behaves.