Will be so worth it though. I imagine the iPad can handle a lot more than the 3GS can. That was a good keynote, lots of things to think about.
I'm one of those not too fussed by lack of 3rd party multitasking and can make do without it. But since we're getting it, I can see me using the iPad for more tasks than before. Flicking between Pages and Safari for example, without actually having to save your document and close Pages, will be great.
Let me elaborate why I think this is a (short term) fail.
Quite simply - the iPhone is less of a productivity device than the iPad. So while it's great that we will be getting 4.0 on the iphone - the ability to multitask and have the upgraded email app alone is reason enough to launch it on the iPad at the same time.