Thanks, Evan! I actually disagree about production use, with similar reasoning to Travis Swicegood's answer about coffeescript in production [1]. Since sibilant is just a source-to-source compiler, it's as production-ready as Node.js or client-side javascript is. The output javascript from sibilant is fairly plain and readable and encourages a particular subset of javascript's features. The language is under active development, but Node's API is also changing. I've been hacking on sibilant since late June and believe it to be sufficiently expressive, although it can always get better.
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[1] http://www.quora.com/Should-I-use-CoffeeScript-for-more-than... .