Admittedly, Dave used to be rather cantankerous, which turned many people off. However, when I was 17, I encountered him in a pizza shop near Harvard, greeted him, and ended up spending the day together.
In 2003, he was working on RSS 2.0, and I contributed a Comments namespace to enable the syndication of comments. This occurred in a more idealistic and less spam-dominated web era. I can still remember the feeling I got when I hit Send to share the proposal with Dave and the community. [2]
Their human-readable and easily understood nature is a byproduct of a time when those qualities mattered. I recall rushing to upload an RSS module to CPAN. It was not simply a conglomeration of other libraries but rather something entirely crafted in my mind.
OPML and RSS are both awesome. They are two standards that have played instrumental roles in maintaining the free flow of information on the web. They were not created by a committee or the IEEE. They were created by someone who was passionate as hell about a free and open web. That's rare now.
1: http://scripting.com/manila/opml/spec.html 2: http://scripting.com/2003/08.html#When:7:12:20AM