I want a Surface device, and not suprisingly I want the SDK. See how easy it will be to develop for XNA and WPF below, you may want one too:
Firefly is an example example of the SDK in use. From what I've heard Surface supports 52 simultaneous multi-touch interactions!
I'm sure there is a killer app waiting to be written with this product.
Below is a great (but noisy) video of some of the demo's recently shown for Surface
Deep Zoom (code name Seadragon) and Surface combined thanks to Live Labs (warning: video below contains annoying advertisement overlays):
The video really demonstrates some of the incredible visualisations you can do using this device. - See here for more videos and news
Some examples of commercial use: