How important are ODP listings to how Google ranks your site? I would guess that at this point not that important for a number of reasons:
1. more than one WebProWorld member has described sites that rank very well in Google but are not listed in ODP
2. Google only infrequently updates its ODP data
3. we all know that ODP is becoming increasingly out of date and overwhelmed by the task of having a human editor personally review every site added to ODP - Google must know this too and this clearly reduces the value of the data ODP provides and will continue to do so the further ODP falls behind
I don't know, in fact, that a listing in ODP has any more weight than a link from any other site to your website - albeit one that has a decent PageRank (what is the
PR for ODP, I wonder...) On the other hand, rumors about "expert sites" being weighted more heavily in future has I think revived interest on the part of Webmasters in being listed in expert sites, which has perhaps provided new interest in finding ways to get ODP listings. However, whatever "expert sites" means (assuming this is in Google's future plans at all), it certainly does not mean only ODP, even if ODP is included in the definition.