The thing is when you are still going to be debugging in a different language, haml -> html, coffee -> js.

As a CoffeeScript guy I think one of its main strengths is its harder to shoot yourself in the foot with is great for beginners but you have to be careful a beginner doesn't just bind all the way down using =>

Actually it IS valuable to have some understanding of assembler, even when you are using JavaScript on a daily basis. Maybe it's not that important for a beginner programmer now, since source maps are available, but I would encourage everyone to go as low-level as possible. Some JS and CS constructs have an awful representation underneath. Think of eval, dynamic types or hashtable-like objects.

No, because C compilers are no longer as buggy as they used to be.