Deal breakers: price, USB, and Apple's attitude
You're very much correct that multitasking vastly improves the potential of the iPad. However, it still isn't up to even the technical capabilities of my phone, let alone a decent netbook.
That aside - the iPad isn't supposed to be a laptop - the big problem for me, in addition to those stated in the article, is Apple themselves. Their attitude regarding the app store, which in itself isn't nearly as open as other platforms' software sources, sucks. As a techie boy, I would not want to have my software choices dictated to me, even in part. If I want to use Opera, Fennec, etc then I bloody well will.
Again, these won't affect the majority of the population, who will regard the software on the iPad simply as a part of the product. But it would certainly affect me, as well as any existing tablet/netbook users with their own software preferences.
As for jailbreaking, sod that. I shouldn't have to re-flash an expensive, premium computing device just to be able to install my own choice of software. I wouldn't accept that on a laptop, or a phone, so why should I accept it on a tablet?