You'd have to already know CoffeeScript and Rails to benefit from this framework. I've used neither so personally I'd have a lot of trouble and a steep learning curve.
This builds on top of two other frameworks (Connect and Express) so I imagine the dependency stack for this framework is really long which might make debugging painful.
This builds on top of two other frameworks (Connect and Express) so I imagine the dependency stack for this framework is really long which might make debugging painful.