Someone with this kind of tenacity seems to be a potentially great "non-technical" cofounder. (Not to be misread as a statement implying that he's a foursquare cofounder.)
You should drop the "potentially." Anyone with the opportunity to work with and learn from Tristan should consider themselves extremely lucky. He's one of the most awesome, humble and driven people I know.
Without "potentially," I'd be describing him as a great non-technical cofounder, which would only be true if he were a cofounder. I am sure that he is an actually, not potentially, great person. :-)
Excellent point.
Agreed. Much lip service is paid to "hustle" but very few actually have it in the way Tristan does.