As much as everyone wants freedom (as in speech not beer) it's not so much fun when your working code is on the line. Even in a 3-week old experimental programming language. Funny that.
It's totally possible that I'm missing the point, but how is _ 0 and _ 1 and better than x and y? Sure this gives you an implicit parameter list, but when you go beyond short functions like add2, wouldn't it be nice to have names for variables? My understanding of [ _ ] was for all those quick, inline anonymous functions, not for function definition of non-trivial functions.
As a casual hobbyist who's trying to learn lisp(cl/scheme), coming from a ruby mindframe, arc actually feels like it may be a net win, while the jury is out on the other two.