One of the greatest features in WPF 4 is the built-in support of Windows 7 multitouch gestures. Developing multitouch applications for Windows 7 you should have a special multitouch screen, and usually you don't have it, at least not in your development laptop. So you have to buy one, or use the PDC 2009 laptop: Acer Aspire 1420P give-away. The problem in such case is that you'll have to use remote-debug to debug your multitouch gestures, and it's awkward. There are several NUI alternatives...