If you want to build the web with Python, IMO the emphasis should be bringing Python to the web. I think a more promising project is http://pypyjs.org/ - a Python runtime in your browser powered by asm.js
I think it's certainly an interesting project, but the goal of compiling to JS today is to be able to access the DOM and interface easily with existing JS infrastructure.
Listen to this podcast where the author describes the project: https://talkpython.fm/episodes/show/32/pypy.js-pypy-python-i...