As someone with lots of Python experience, having used CoffeeScript/JS for ~three months makes Python looks somewhat old fashioned when I switch back. If Coffee/JS had some way of overloading array access operations, and maybe a numpy equivalent, I don't think I would have any reason to go back to Python. It's also just so much faster than CPython...
I actually quite like Javascript, especially for its speed. However, the major obstacle to me is that JS is locked in web development. It even does not have a standardized module to read files line by line, let alone other system-level stuffs. One of the (small) reasons that python is not used in web browsers is the lack of speed.
The upcoming version of JavaScript--some engines already support this, I think--includes support for "proxies" which basically let you overload both array access (a['b']) and . access (a.b) for an object.
