I agree. For most people, a 10" tablet is a toy. With no tactile feedback, no serious typing can be done.
I think that this rumored product's main purpose will be to drive AppStore purchases. Playing some of those games on the larger 10" screen would appeal to some peoplenot me though.
In my experience (some iPT use, lots of Nokia N800 and N810 use, some netbook use), what I need to do while out and about (on the bus, waiting for food at a restaurant, very light email responses, making notes on my RSS feeds, etc.) is fine with thumb typing, and would probably be fine with the right thumb keyboard (N800 and Apple lose here, because they obscure the app, but N810 worked because it doesn't ... a 10" iPT might work, if you can see the actual application in the "top" half of the screen).
For serious typing, though (which, in my experience, I only needed to do in places like meetings, where I have a table available), you're going to want a physical non-thumb keyboard. Physical because of the tactile feel of the keys (not just the press, but the feel of knowing you're actually ON a key, and not straddling keys), and non-thumb because many fingers is faster than 2 fingers (it really is). A netbook is one way to do that. Another way to do it is with a tablet and a 10"-12" keyboard ... like the Apple Bluetooth keyboard ... or like the brand new Apple USB keyboard that looks just like the Bluetooth keyboard. Prop the tablet up on a table, plug in the new USB keyboard, and type.
(be careful of your keyboard choice though ... the Apple Bluetooth is nice and stable, but I had a stow-away iGo bluetooth keyboard, and it had a tendency to want to rock a little when I hit keys at the extreme ends of the keyboard... that made it difficult to type full speed; it was also a 4 row model, so there was a lot of meta-key action if you wanted to type numbers; make sure whatever keyboard you get is stable and has 5 or 6 rows)
