I have thoughts, they are a bit cynical, but don't take offense, my bitterness is certainly not aimed at you.
1) I couldn't care less if there is any grphical response, but I can pretty much guarantee you that a display isn't going to last anywhere near as long as the simple lexan touchpads we have enjoyed for so long have (and could continue to), plus it is glossy and therefor probably not as easy to glide on, so you would have to add and deal with something like 3M Vikuti screen protection sheets (which have a texture more like our keyboards, and are specifically made for devices where you write on the screen with a stylus, but work great for finger touch applications as well, in my experience), assuming these didn't disrupt the multitouch technology.
2) One would have to buy two iPads and the app would have to be customizable enough to make each iPad half of a dvorak layout for this to be the least bit interesting to me (ideally, it would allow for every gesture I have been using for so long, as otherwise I don't have anything but a toy to show off, and I don't even know if iPads would support palm and side of hand gestures at all, and seeing as how the two pads wouldn't communicate with one another, the chord functionality would either not exist or behave in undesired ways). Regardless, while the price of 2 iPads pretty much seems reasonable anymore bosed on what touchstreams go for on e-Bay, it doesn't seem so reasonable when you consider that their contsant use will probably wear them out in short order.
3) These two iPads will either be running on battery and connected via bluetooth, in which case you have a keyboard that has batteries that die at least once a week, maybe every two days, that also has connectivity issues, or they will be connected to the computer via USB and possible also connected to a separate power source, in which case you end up with at least two, maybe four separate cables to make everything work, what a mess. Moreover, who is to say you won't have other funky issues since there are technically two keyboards that don't communicate with each other).
4) I don't want tactile feedback, and I certainly don't want sound feedback, but having little bumps on the home row sure is useful, the iPad isn't going to have that since it is not a keyboard.
5) I'd simply much rather buy a device from a small third party company than pass any of my money on to the corporation that is Apple, who will buy patents just so someone else can't use them, and who will severely restrict the potential possibilities of any device they make through their licensing and software channels (think AT&T only iPhones that get bricked when you try to jailbreak them and otherwise don't allow apps not approved by [and therefore also funding] said corporation). If I buy a tablet sized device, I should be able to do whatever I want to it, and Apple shouldn't know jack about what I'm doing to it unless I feel like letting them.
6) Good luck leaving an iPad or two sitting on your desk, everyone will know they are worth money and they will disappear in the blink of an eye, just like even the cheapest iPods do. At least with the touchstream (or any other keyboard, regardless of price), no one realizes what they are worth (and in many cases, only those who own them even know how to use them), so there isn't a thriving black market.