I really want to create a stunning-looking GUI desktop application that looks like, for example:
Regardless of the UI technology, you will of course be well-served to adopt a programming style where the look and logic of the app are as decoupled as possible. This allows you maximal flexibility to design and evolve the look of your application (the View) while potentially requiring very few code changes in the back-end (the Model or ViewModel).
While possible using all UI technologies, it's particularly easy to execute this in the case of WPF/Silverlight/Moonlight via the MVVM programming style, due to the succinctness of databinding (very little boilerplate "glue" code).