WPF is very complex. The learning curve is extremely steep. The (early/lack of) evolution of the .NET runtime and the C# language also made WPF more difficult t

WPF is very complex. The learning curve is extremely steep. The (early/lack of) evolution of the .NET runtime and the C# language also made WPF more difficult than it would be if it were created today. And, finally, Microsoft never bought into it fully. That said, it is, by far, the best desktop UI library for Windows-only apps. I wouldn't consider using anything else until/unless the following were equal to WPF. The amount of engineering gone into the framework, the thoughtful design, the critical mass of use.