I recently watched a session taken from the Professional Developers Conference 2008 in which they describe the various ways developers can integrate touch into their applications. One of the great things about Windows 7 is the out-of-the-box support it provides for legacy applications that do not include explicit support for touch gestures. For instance, applications running on Windows 7 will automatically receive support for pan, zoom, and right-click gestures, as well as controls with standard scrollbars.
With minimal effort, a developer can include additional features in their applications by taking advantage of the API, such as gesture notifications and events for pan, zoom, and rotate, inertia configuration, and P/Invoke. As an example, you can pass the parameters that you receive from the notification into the WM_GESTURECOMMAND API, and it hands you back a gesture info struct. The struct includes information on the specific command received (was it a zoom, pan, or something else?), arguments that are specific to the type of gesture command (if it was a zoom, how far did the user zoom?), and the location over which the gesture was centered.
And to take it one step further, a developer can build an application with touch in mind from the ground-up, and in so doing, take advantage of features such as raw touch data, manipulation and inertia processors, touch events, and real-time stylus or ink collector classes. Mobile, desktop, and Web applications that incorporate advanced touch features will provide a richer user experience that will set them apart from those applications that do not.
If you want to learn more about developing multi-touch applications for Windows 7, then a great place to start is by watching the Windows 7: Developing Multi-touch Applications session from PDC2008 (http://channel9.msdn.com/pdc2008/PC03/).