I'm not a fan of RubyJS, but I dislike underscore for the same reason: it encourages people to use implementation specific versions fo existing ES5 standard methods [1].

I use ES5 shim instead. That way when I ditch support for IE8, I don't have to fix anything.

[1] Obviously Underscore doesn't have methods, it has utility functions attached to punctuation.

You might not feel it's necessary for you, but I don't see the need for the critical tone.

They've donated their time to add something new to the ecosystem. You are under no obligation to use it.

This looks like a neat combination of Underscore/LoDash and Cofeescript to me. It's good that people are trying to come up with new stuff.

underscorejs didn't provide me String methods, Time (with timezones), some number methods, and a few iterator methods i was used to from ruby land. Also i missed the chainability across types and iterators.