I have an affinity for python, but I work in a .NET environment, so I was looking into Iron Python, and wondering what it would be used for.  
Could you write an app in it? or is it for adding a scripting language to your app?
How do you guys use it?
You can write an app in it, you can use it as a scripting language in your app.
It's used for accessing existing Python libraries and, if needed, writing parts of your code in Python if a .NET languages doesn't seem well enough suited for that job.
Iron Python : what are good uses for Iron Python