The most common use is adding an extension environment to .NET apps, which is very, very easy with the DLR. Big frameworks don't fully work, primarily because

The most common use is adding an extension environment to .NET apps, which is very, very easy with the DLR. Big frameworks don't fully work, primarily because IronPython uses Unicode strings everywhere (like Python 3). We are working to improve compatibility as much as possible though, and moving to 3.0 will really help.