Nobody in their right mind uses this stuff in production code.
It just overcomes objections. "Oh, if I start using Lisp, there is be a way to use infix, should I really need it". Ten years and six Lisp project later, you still haven't used the infix stuff; the situation never comes.
You sure about that? I thought the lispy approach was generally pragmatic - you use what you deem handy for your application. It this weren't the case, there would be little need for macros in the first place. I can very well imagine, say, a scientific or engineering application that would share a common infix parser for both user-provided expressions (in the UI, to be more friendly to non-lispers) and heavy math lifting in the source code.