The WPF ah-ha Moment

In nearly every bit of WPF training material or weblog there is some reference to the "ah-ha" moment. The point at which all the new concepts you've been learning gel into a cohesive unit. For me, that moment was one or two months after I started developing WPF in earnest (by which I mean for users other than myself). The task was to display two different indicators of a business metric, a green up arrow and a red down arrow.