Bringing an existing .coffee code base across from Rails is an annoyance and I would prefer to standardise with the implied form as we are using it everywhere else. It's obvious that .coffee requires the extension .js and it's more DRY.
The only potential issue is if you wanted to keep .coffee files within the project that would not be compiled which might be the case for some blogs (although we are using Stasis for making Chrome extensions).
Rails/Sprockets already supports this.
Add use default extensions for scss and coffee
Set a default extension for SCSS and CoffeScript files if infix
extension is lacking, such as in application.scss or application.coffee
instead of application.css.scss or application.js.coffee.
This also addresses issue #38