You can't run more than one app at once, which is annoying. But rumor has it that that will change when the iPhone 4.0 software is released this summer.
So how would multitasking work? Similar to Expose in OS X. Hit the home button twice and all of your apps will spread out as small icons across your screen. Tap one to go to it. It's a pretty easy.
Would you do it differently? On Android, you can pull a menu down from the top of the window to access things like text messages, so you don't need to leave your app at all. It's an elegant solution. What are you looking for in iPhone 4.0?
Via Apple Insider