I've used a non-multitasking phone and found it mildly irritating, a full computer like that would be a pretty toy, not a tool.
As the pre-sales show, there is a good market for pretty toys, bought a few myself, but not from Apple.
I have a Sony ebook reader, which has an essentially infinite battery life and weighs very little. If I drop it, it does not break (tested the hard way), and if it does break, it's cheap enough that my heart does not break with it.
I don't need (or even really want) windows on a handheld, but existing mobile Windows falls below what I require in functionality, the iPad has less functionality than that.
I'm a mobile worker, sometimes it can be weeks between getting to base, so ought to be the primary target for business use, but I can't see how I could go more than a day or so with the iPad without needing a real computer.
If there is a clusterfuck over this, I think it's going to be warranty arguments....
I take it we all know that robustness and strength goes up as the square of dimensions, but weight goes up as the cube.
That means a device which in some ways a scaled up iPhone won't be as tolerant of drops and other impacts. I'd bet serious money there is an "impact sensor" in the iPad, just like the famously over sensitive moisture sensor in the iPhone.
People will find that their shiny new toy has stopped working and will be told "you dropped it sir, sorry". Some will have dropped it, to be sure, but I think we know that the sensor will be set to a level that voids as many warranties as Apple thinks they can get away with.