It's less broken, say, than Twitter, where many legacy non-#! links became redirects to #! links.
But the whole thing is like the thinking that "This site works best with IE 5.0" -and, naturally, is crippled for everyone else- is a reasonable approach to web design. And at least those sites warned us about what the pain they caused and why - this UI is more like visiting a Flash-only webpage in 1998.
Have these guys never heard of the noscript tag? No, wait: weirdly enough, Bret Victor actually uses the noscript tag to govern which CSS file is loaded. That is, no doubt, why the featureless black webpage I am presented with is so uniquely appealing a featureless black webpage.
Telling NotScripts to temporarily allow Javascript to look at the site shows a website with very nice graphic design and awful usability. Which is very much what I expected.
Javascript often offers the same usability experience as Flash. That's why I disable it by default.