I get what you and others are saying about this, but you can't read an email and an eBook at the same time, or look at a map or video while still reading the website, or take a photo while simultaneously playing a game. All of these activities, even on a multitasking computer, require that you bring a certain application to the front and focus your attention on that application, while momentarily ignoring the other. If the apps close and reopen instantly alá the iPhone with the Home button, and resume right where you last left off (Kindle, Maps, Safari, Mail all behave this way) then what's the difference if they were still "running" in the background or not?
The music playing in the background business remains to be seen. I generally stick with my own music synced from iTunes, mostly because it really is my own personal Pandora, but also admittedly because of the fact that I can't stream the real Pandora in the background. I have to believe the iPad will at least allow for iTunes to play behind other apps, just like the iPhone does. Allowing audio streams from 3rd party apps across the platform would be a nice addition.