Do you mean "ODP search on dmoz.org" or "ODP ssearch on directory.google.com"?
If you are talking about dmoz.org: I don't think the ranking influences anything. There is some rather unknown algorithm behind the search. Since it's not even completely known to the current staff members, it's highly unlikely to influence anything outside ODP. It does not influence how data is stored in the downloadable RDF file, anyway. So datta users won't be notified of the "ranking"
Iff you are talking about the google directory: Well, its sorted by PR, and PR is still known to influence rankings on Google. And maybe on other SE as well.
ODP search is driven by an open-source text indexing program someone picked up and modified to work with the ODP RDF. Its search results order is deterministic but indeterminate. (That is, it seems to be always the same order, but there's no predicting what it is.)
It is a misnomer to call it "rank"; it takes into account whether or not all the words occur in ODP description, title, or URL -- a binary function -- and nothing else you can control. (Which is probably a good thing: otherwise, people would be submitting frivolous or malicious "URL update" requests to try to control it.)
Simple? Yes. Unsophisticated by the site-search standards of, um, seven years ago? Yes. Useful? To editors, definitely; to surfers, perhaps sometimes. Not as good as Google directory search? Um, well, OK, if you say so.