There's a better set of tools than using Windows Presentation Foundation (WPF) straight out of the box: WPF plus Prism (formerly "Composite Application Guidance for WPF and Silverlight") and Unity.

If you're building Windows Presentation Foundation applications that will change over time or have some combination of complex workflows, rich user interaction, and significant presentation or ...

Microsoft released a new version of Windows Presentation Foundation, their next generation windows application UI framework. The new version will ship as part of the .NET Framework 3.5 Service Pack 1.