Here is another video from last week. It's a new Eee touchscreen PC. It looks like it is single-touch, but it has a couple of nice NUI applications.
Post-it application (0:45)
The post-it application has good animated transitions that make it easy to understand what your should be doing. You're often working with the content directly. One possible issue though is whether changing from the clock to the post-it page requires a swipe from that button on the bottom or not. If it does, how does the user figure that out? It would be better as a two-position slider than a button.
The demonstrator seems to not be 100% familiar with the application gestures, since, for example, sometimes he launched the post-it app with a single tap and other times with a double tap. Also he couldn't figure out how to get back to the clock from the post-it mode without resetting the app. (Did it require a swipe to the right?)
Regarding accidental double-taps, many users coming from WIMP may have the urge, as in this video, to double-tap to launch or activate an icon. NUI applications have to account for this and 1) not have different behavior for a single vs. double tap on the same element, and 2) account for what will happen if the user taps an interface element more than once before the action completes. This is a good argument for making the interface respond instantly, particularly if the requested action will take some time to process.
Media application (2:45)
Another good detail is in the media application, which was designed for touch, notice the minimize and close (X) buttons are extra-large, good targets for the finger. Much of the rest of the video shows regular Windows (WIMP) applications, which respond to touch, but aren't optimized.
On screen keyboard (4:05)
Allowing the keyboard to resize might be good for adjusting to different screen resolutions and hand sizes, but the screen form-factor doesn't seem to be optimal for touch-typing and regular keyboards are one-size fits all, so the resizing may not be that useful.
The www and smileycon keys are good ideas to save time, considering on-screen typing won't be as fast as with a keyboard. The hold-flick to capitalize seems a bit buggy and slow. I'd probably stick with a shift key if I were using it, but with only single touch it'd have to be a sticky shift key.