WPF is a mature technology. It’s been part of several releases of .NET, with steady enhancements along the way:

•  WPF 3.0: The first version of WPF was released with two other new technologies:
  Windows Communication Foundation (WCF) and Windows Workflow Foundation
  (WF). Together, these three technologies were called the .NET Framework 3.0.
• WPF 3.5: A year later, a new version of WPF was released as part of the .NET
  Framework 3.5. The new features in WPF are mostly minor refinements, including
  bug fixes and performance improvements.
• WPF 3.5 SP1: When the .NET Framework Service Pack 1 (SP1) was released, the
  designers of WPF had a chance to slip in a few new features, such as slick graphical
  effects (courtesy of pixel shaders) and the sophisticated DataGrid control.
• • WPF 4: This release added a number of refinements, including better text rendering,
  more natural animation, and support for multitouch.
• WPF 4.5: The latest version of WPF has the fewest changes yet, which reflects its
  status as a mature technology. Along with the usual bug fixes and performance
  tweaks, WPF 4.5 adds a number of refinements to that data binding system,
  including improvements to data binding expressions, virtualization, support for the
  INotifyDataError interface, and data view synchronization.