I saw you implemented function composition as what seems like 'symbol hack'. I don't know what to think about it... But in the same vein, I thought it could be possible to do the same for gensyms in macros. Something like prefixing hygienic macro variables with @
I like this idea (and the character you chose: @), but as zunz points out in http://arclanguage.org/item?id=105 , it would be convenient in some cases to have all symbols resolve at the macro definition site, rather than at the use site, except for those specified otherwise (for instance 'it' in the aif definition). If I understand correctly, this is all that hygienic macros require.
Hygiene does have the drawback that you can't bugfix a function used in a macro definition and have it just work, and that might well be more important in a language which is so young. I only mention this because I just did this, and if it hadn't worked I'd have been surprised. But that could be because most of my lisp experience is CL, rather than Scheme.