Touchscreens are fine and dandy for iPhones, LG Dares, and the plethora of other touchscreen phones because it doesn't seem out of the ordinary to control these hand-held devices with your finger. With desktops or laptops on the other hand, the mouse and keyboard just feel more natural -- not to mention that your fingers are inefficient on the larger platform.
The fact of the matter is that scrolling, clicking (especially right-clicking), and the handwriting feature on a Windows 7-equipped touchscreen are frustrating at best and futile at worst. It may be good for a quick laugh or some fun when you’re bored, but the novelty will wear off (and it's definitely not conducive to productivity). If you haven't tried any of these features with a touchscreen PC, try running over to a local Best Buy; they usually have one on display for you to play around with.
But here’s my criticism of the common criticism, if you will: Just because a few novelty features don't work that well doesn't mean that you should judge the entire system as a failure. For example, I own an LG Dare (a touchscreen phone), and it includes an option to handwrite text messages. That method is slow, and 30% of the time, the letters I write are misrepresented. In short, it’s a feature I don’t use because it doesn't work well. Now, does this discount the entire touchscreen phone as a whole? Definitely not.
The touchscreen features of Windows 7 that you will really want to focus on are the zoom, the pan, and the rotate features. These features tend to be difficult to execute with a mouse, and can’t be done easily by a keyboard. So using a quick finger swipe to rotate a photo or zoom in on a website, while reading and scrolling with the mouse, for example, could turn out to be very efficient in come centexts. Basically, your fingertips can come in handy in the cases where a mouse and keyboard come up short.
So all in all, despite all of the negative reviews of the touchscreen features, Windows 7 will still be a serious contender in the market given all of the innovation it has put into its touchscreen. The touchscreen will definitely not replace the mouse or keyboard, but the usefulness lies in its ability to interact with the mouse and keyboard, rather than to replace them.