About the only thing this looks good for is being an over-large remote control for other gadgets and applications. For example, it could be used to control your music software, with virtual faders and knobs, like a cheaper Lemur. But even then the inconvenience of the form factor means you are likely to get RSI pretty quickly. (Being a long-time sufferer, I never joke about RSI.)
But besides, a touch screen is simply no substitute for a real button or a real knob. Or a real keyboard or phone pad for that matter. There's no feedback. No resistance. Limited affordance, as they say in the UI business.
If you want a handier software-controlled touch screen remote, well, I hear the iPhone already exists. As a bonus you can take calls from your clients when you're not mixing.
If I want to do nothing but surf the web I can buy a netbook for half the price. I won't be locked into iTunes, I will have a real keyboard and Flash websites will actually be viewable. (Apple has an issue with Flash so they've ruled none of us get to see it.) No touch screen, but so what? I've got real ports and a card reader and a real OS (LINUX in my case).
Yet people will buy the iPad, because it's nice and shiny and has conspicuous consumption written all over it.
Or am I missing what this thing is useful for? Besides turning Apple a huge profit I mean.
(Next time I'm going to kvetch about Windows 7. I'm sure you can hardly wait.)