"Anyhow, someone at Microsoft needs to wake up. Great idea, poor execution."
That's a little harsh. From my experience with WPF, including Windows Forms interop, WPF is great at two things: 1) completely redesigning an application to be form-less, and 2) using visual cues (animation, transparency, etc.) to enhance the UI in a traditional
application. I agree that it's not as mature as Windows Forms (or Win32), but that's to be expected given it's age.
My guess for the reason why you're not seeing a lot of WPF source for LOB apps floating around is that UI controls are moving from being a commodity (i.e. a ComboBox = ComboBox = ComboBox) to being a differentiator.