It's funny, just today I finished up some work merging a hygienic expander into the core of Guile. I've been writing defmacros for a few years now, and while things are not all lovely in the world of syntax-rules or syntax-case, it is so much more lovely to write a macro that you know catches the important cases, and that will compose well with other code, and /especially/ code from other modules.

That said, have fun with Arc ;-)