If the only thing WPF offered was hardware acceleration through DirectX, it would be a compelling improvement, but not a revolutionary one. But WPF actually includes a basket of high-level services designed for application programmers.
Here's a list with some of the most dramatic changes that WPF ushers into the Windows programming world:
A web-like layout model. Rather than fix controls in place with specific coordinates, WPF emphasizes flexible flow layout that arranges controls based on their content. The result is a user interface that can adapt to show highly dynamic content or different languages.
A rich drawing model. Rather than painting pixels, in WPF you deal with primitives—basic shapes, blocks of text, and ...