Really? I find netbooks to be less usable than traditional laptops and desktops precisely because of the keyboard. Granted, the only netbooks I've tried are 9-inch Eee PCs made by Acer. Are the keyboards on 10-inch machines that much better?
From having owned both 9 and 10 inch Eees (still got the 10, lovely machine) - the 9 was perfectly manageable for me but the 10 I'm as fast as I am anywhere. I regularly use it to take sermon notes at church and have before been able to keep up fast enough to produce a readable (if a little abbreviated) version of the presenters' material, because a friend used it for exactly that.
Now, I'm probably a bit unusual there and I could've sold tickets to some from their expressions watching me concentrating on the speaker as my fingers flew across the keyboard, but I don't see typing on a 10" netbook as any hardship at all.
I've never tried using a tablet computer, but I think these will suffer from ergonomic difficulties. For situations such as reading books/text or maybe browsing the web from a sofa they would probably be ok, but most web content isn't designed in such a way as to make the links/buttons large enough for a finger. On a touch screen the UI design needs to be quite different from those which are intended to be mouse-driven.
Also take a look around the various exhibitions and see how many visitors are carrying tablets with them as opposed to laptops or netbooks. That's probably a fair indication of how useful tablets actually are.