In my opinion, one of the biggest differences between programming in WinForms and WPF is how much you use data binding. WPF programs typically make heavy use of data binding, but many WinForms apps do not use it nearly as much.
I just published an article on CodeProject that is intended to help people with WinForms and ASP.NET backgrounds to start thinking in terms of WPF data binding. It walks you through four iterations of the same simple app: going from all code with no data binding to all XAML with data binding.
If you want to check it out, here’s the URL: