There is no compulsion whatsoever to use the touch features. That is only one part (albeit pretty important and cool) to the X2 story. If anything, the touch support helped improve some of the mouse oriented features such as scrolling in the prochannel. There are plenty of other features, enhancements and stability improvements that Make X2A a huge update even without considering touch.
Regarding touch, once you have used a tablet you will see that there are some gestures that are far more efficiently done than with a mouse. Scrolling, zooming, and multitouch operations if done well make it hard to go back to using a mouse when touch is available. Multi-touch is in the future for all portable computers and in a year or so you will likely be hard pressed to find one without touch support. Its one of the most important UX features we chose to support for the next generation of PC's.