During the demonstration, Scott Forstall indicated that apps in the background enter a "quiescent state, using no CPU" on the device. How is this multitasking? Apple is completely suspending any background apps, while allowing only specific background processes (local notification, location, audio, etc.) to run. For example, I'd like Tweetie to download tweets in the background, or NetNewsWire to download articles in the background. From the presentation, it looks like the only way this could occur in the background is for me to launch the app, manually begin downloading data, and then exit to some other app or the task manager. If those apps utilize the task completion feature in OS 4, they'll finish on their own. That's OK, but I'd much rather have them downloading that data at predetermined intervals, like a mail client does. If we had true multitasking, those apps would actually be running in the background, and could do this.
On a totally unrelated note, how do we quit apps in the new task manager? Hold down the icon until we get an "x" in the upper left corner of the icon? I didn't see any differentiation in the presentation between switching and app and closing an app.