C# .NET 3.5 GUI design

Windows Presentation Foundation is a vector-based system that is part of .NET 3.0. It allows you to define your UI in XAML, and can do all sorts of animation, 3D, etc. very easily. It's much newer and still being evalulated by a lot of folks.

Windows Forms is a wrapper over older windows UI classes (Win32/MFC or whatever). It came with .NET 1.0 and uses C# to define all the UI and its layout. It's the tried and true UI method.

Chris Sells seems to be 'dah man' with regard to Windows Forms and WPF:

http://www.sellsbrothers.com/writing/
http://www.sellsbrothers.com/writing/wfbook
http://www.sellsbrothers.com/writing/wpfbook

Also well taking a look at Charles Petzold as well:

http://www.charlespetzold.com/winforms/index.html

MS also have a heap of stuff related to design guidelines and usability from a windows perspective:

http://msdn.microsoft.com/en-us/library/aa152962.aspx

WPF is a totally a different and a new way to look in to the UI architecting and implementation. The cool concept of collaborative development by a designer and C# developer is a biggest advantage(XAML markup actually gives this ability). When you develop a control/UI it will be in a 'lookless' manner and Designer/Integrator can take that same project(XAML) and style it for a greater look and feel. So in short WPF or Silverlight is a paradign shift in the way we do winforms development.

So .NET3.5 UI design can be done in two ways. 1) Winforms way 2) WPF-XAML way. I think for a futuristic and modern UI you definitely need WPF than winforms.