I too have used H2G2 -- years before it was aquired by the BBC. I wrote the Sweet Tea and Gnat Line entries in fact. Back then (and perhaps even now), the writing process was unidirectional: An average joe would write an entry and submit it as a potential official entry. Then, a person in the role of editor would come along, make vast sweeping changes, and publish it, without letting the author give input or corrections about the editor's changes. My Sweet Tea entry only has a few "unauthorized" changes, but the Gnat Line entry is only vaguely similar to what I wrote ages ago. Gnats are "a kind of blood-sucking fly"? Ha!
I don't think of it as very Wiki-ish. It's too edited. Too immutable. Too much like a moderated bulletin-board without the good organization. The web's progress has made H2G2 obselete; H2G2 could never be as good as a WikiPedia.