I especially like the way it wraps the expressions you want in infix and doesn't affect ones outside of its body, allowing you to use infix syntax in one place and not make the rest of the program behave in unexpected ways.
This will be especially good one we can bring readtable support (or the equivalent) into arc. I saw this suggestion somewhere:
<3 + 4 * 5> ; syntax for an infix math form.
And as you say, BNF parsers and whatever the notation for scanners is will be great.
