I've been noodling on structural editing for a while now. I'm fully bought into Lisps myself, but most of my friends and coworkers are skeptical, and I think a lot of their skepticism has to do (as usual) with all the parens. One of the points I make frequently is that with Lisp code being written as a nested data structure, the textual representation is just one of many possible representations. But it can be hard to get across what that means without concrete examples.