The page itself is set in the proportional version of Go. I found it distracting to read because of the uneven character widths. The majority of the characters (like 'b', 'd', 'f', 'k', 'l', 'o', and 't') are narrow, but some common letters (mainly the 'e' and 'c') are round and wide, with generous space around them. I can't get past the impression that I'm reading paper that wrinkled when it went through the printer. Even the name "Go" has a wide G, awkwardly large space, and narrow "o". Perhaps it's an artifact of the browser rendering, because it's less noticeable on the alphabet sample image.
The monospaced example reminds me of TeX-produced CS papers at first glance. I'll have to give it some time.