Neel Krishnaswami explains how Heroquest turns setting into rules effortlessly.
In one of the comments on that article, Brand Robins said:
I just remembered something I said to my Grave of Honor (A Game of Thrones with HeroQuest rules) group when we got started: "HeroQuest is really, really good at supporting your vision. If you know what you are doing, have a feeling for what you want, and push your narration then HeroQuest will support you better than just about anything else. If you don't have a good vision or feel, however, or if you're looking to have the system tell you what happens or suggest courses of action seperate from naration (as most games do) then you're going to be SOL."
All of my actual play with the system has backed that up in my experience. When you go into HQ with a vision, a good flow of narration, and an understanding of what you are after it supports you brilliantly. It does not, however, particularly help you in developing those things if you don't already have them. Thus the frequent complaints (on RPG.net and similar) that it breaks down into a "bean counting game."
In an entry on his blog, Brand Robins talks about medium length/detail contests in HeroQuest.