Very few sites are "cooled" in the ODP. I don't think it has any effect on PR.
But, from the ODP Editor Guidelines:
"Editors may not cool their own sites or any sites with which they are affiliated, including business or personal affiliations. Doing so is contrary to ODP's policy and mission to provide a fair and objective resource for end-users. It is also contrary to this policy to request another editor to cool a site with which you are affiliated. Misuse of the cool site feature may result in removal of your editing privileges. Please see the section on Conflicts of Interest for further explanations."
From the conflict of interests section:
"In some cases, an editor's business affiliation overlaps their involvement in the directory, such as with Search Engine Optimization (SEO) professionals and Professional Content Providers (PCPs), whose participation may benefit both the editor and the directory. Instances when the involvement is mutually beneficial are acceptable, however, the primary focus and goal should always be to serve the best interests of the ODP and the editing community. Conducting unfair and deceptive activities to promote and support client listings will result in removal of editing privileges."
As Enron & others proved there are always a few bad apples in any cart. But generally most editors keep to these guidelines :) Probably more would if the guideline manual wasn't so huge ;)
In most categories there isn't one outstanding site which deserves to be cooled. I've never cooled any site....I' just plain mean at heart :)
I see a lot of people talking about the influence of the ODP. As far as I can tell it only has a major advantage if you happen to be in a category close to the top of the tree. If your site is in one of the categories towards the bottom (like all the regional stuff) it doesn't do much for you at all. Try following the regional category down to the bottom and see how many sites appear in the Google/ODP directories but are not indexed by Google at all (they have been there for months). The lower limbs of the tree have a low PR value, the sites in them get no advantage.
If you have a site that should/deserves to be in a high level category then the PR value from this source can be significant. I just found a few PR 6's that seem to get it purely from the ODP/Google directory :( ...giving to much power to a few for no good reason IMHO.
The influence I am more interested in is related to the description applied from the ODP. Having keywords at the start of the ODP description definately seems to help (not with PR) but with rank. If you have the PR already and got "lucky" with the description from the ODP then life is good.
This element seems to be exactly the same as the Y directory search works, although I don't see much future in the Y directory now. Remember the old days (last month) when getting the number one site in Y was as simple as a decent PR, a domain name of widgets-widgets-widgets.com and a description of "Wholesale provider of Widgets to Widget resellers"? At least G doesn't seem to give preference because of the domain name.
ODP editors are not supposed to repeat any of the category title (usually has the primary keywords) in the description. But some dscriptions get between the cracks, especially where there are several good keywords for a product or service that don't appear in the title of the category.
e.g. If the category was "Useful Gadgets" a description of "Widget suppliers offering online ordering" would typically get in. If the primary keyword is Widgets Google now seems to give preference to that site because it is in the ODP description. Of course it still needs a PR close to the competition and needs to be optimized at least almost as well as the competition (or contain the word widgets 100 times :( please develop a spam checker G ;)
I have seen this "description" problem in numerous categories. Personally I would like to see Google ignore the ODP description, display it, but don't use it for anything else.
Maybe they are doing some of the above - that's why this update is taking so long to come to the boil ;)