I don't believe DMOZ gains you a lot of growth. It's more about your website's reputation. If it's listed in DMOZ than it's worthy to be visited. But there are some rumors, that DMOZ and Yahoo listings help in higher SERP.

I also think same but you can get a strong higher PR backlink which contribute in ranking website high. But believe me when it is listed My website jumped to 6th position on google uk from 21st position in the very next day against "UK Magazines".

I have this pot in all webmaster forums where I am a member..

Essentially a DMOZ listing is just a link found within a directory and it sits in a pool of hundreds of thousands of other directories that generally do just about the same thing.

As Google is the owner of DMOZ it stands to reason that the search engine will trust and thus reward the links contained within DMOZ pages moreso than it will when it finds the links found within the other standard directory type web sites but I wouldn't think that it would be anything substantial in most cases. I could see that in some keyphrase competitions that it could play more of a ranking factor than in others but that would not be the standard across the SERPs board.

If DMOZ listed links can do such wonders, then i think it is a good option to buy some already dmoz listed expired domains. Of course will need to some research on those domains before buying.

I hope there are many other factors that could have influenced the ranking but surely dmoz is not the single factor.

Yes, there are many various factors which help a site get traffic, and of course getting approval from Dmoz is also a big help. This is one of the most famous site, so when your site is accepted it means yours is really good. That's why you can see the change in ranking. I know this; however, it's really hard to have our site approved in Dmoz. I can't do that

I haven't heard dmoz mentioned in the longest time. Is it still as powerful as it used to be ... or am I just out of the loop?

DMOZ will approve your site once you follow their rules in submitting site. I have also 2 blogs which was listed in DMOZ.