I have worked with WPF on a couple of applications (one LOB, one controller UI) and I find it is very elegant and a productive tool to use. The databinding and nested control element container model are very powerful.
It is very different from Winforms and has a big learning curve. Once you have made some progress along that learning curve, though, you will never go back to WinForms - at this point when I think of using WinForms I think, "ugh!"
