By way of context, I was a test subject for a perhaps related project called Code Bubbles http://www.andrewbragdon.com/codebubbles_site.asp a while ago. Since it was for Java, a language which is comparatively verbose and I often have difficulty getting decent code density with, this new IDE interaction was truly novel and I found often useful.
I test drove the Pretty Lisp Demo and felt myself wanting for code density in a language where I don't typically have those issues. It was just too hard to fit a useful quantity of code in a screen.