Judging by typeface design, samples, and description, the font isn't designed for body copy. Also, right now on the page font samples themselves play the role of “huge, super thin headline”—having more than one of these usually is not a good idea from visual design standpoint, so I wouldn't use it for headline as well with current layout.

That said, it would make perfect sense to have headline set in Subtle Sans, but with larger font size and font samples moved to a less prominent place.

By the way, the Download button actually uses Subtle Sans (not the best place for it IMO though).

Typeface is important, but not as much as knowing how to use it properly. In this regard, typographic solution from Twitter Bootstrap brought a very nice change to the world of ‘developer-built’ websites appearance.

It's a display face. It doesn't even have lowercase letters.