Of course, Sweet.js provides means for breaking hygiene.

Also, Clojure macros are kind-of, a-little-bit hygienic, with their rules for identifiers resolution.

Anyway, I'd say they're rather similar in expressivity and capabilities, but I don't know both macro systems well enough to do detailed comparison.

Right, in general languages without any means of syntactic abstraction feel contrived to me now, and after working with several macro-enabled languages I really want to have support for them in more places. JS (Sweet.js), along with Dylan and Nimrod (and others) showed that it's possible to have real macros in non-prefix languages - I wonder how long it will take the "mainstream" to become comfortable with this feature. It looks like it takes anywhere between 20 to 40 years on average for concepts to "enter mainstream", so I think we're going to have to wait quite a long time yet.