I would say adobe air is Adobe's answer to click once deployment. Also included, this give a way for flash designers to extened there web applications as desktop applications such as twhril for twitter. Microsoft's answer back will be the Silverlight 3 which should be availible next month.
To me I don't think there is much differnce beside letting a web developer run their applications on the desktop vs a desktop developer trying to customize there app for the web. All in all I say its just another flavor of a thin client.
