Glad to find a nice link to a great demo of IronPython from Jim Hugunin.

In version 1 of WPF, we chose to not enable scripting scenarios, but instead require you to compile any code. At least that is what we thought...the demo shows:

"interactive exploration and GUI building from a command prompt as well as simple embedding as a scripting language in an existing Windows Presentation Foundation application."

It even shows loading some UI using XAML from IronPython code.
Love it!