We own an OV Penthouse at Ko'Olina.
The great thing is that you'll always be assigned a Penthouse.
In the new Hale Moana (building 2), the OV's are on the top 16th floor. In june we had 21608 Guest Suite lockout only and the view was fantastic. The following week, we were in 1017 Master Suite in Hale Kona (building 1).
In Hale Kona, OV's are on the 8th & 10th floors, right up front. True, there aren't many OV's and less IV's, but we have never had a problem reserving.
The ONLY difference I know of, is that the OV Penthouse has higher ceilings. Any Villa directly below the Penthouse will have nearly the same view, but one cannot be assured of an assignment to one of those.
We have never exchanged it, but believe that there is no distinction with Interval. Just the lucky person who gets it will be happy. (One loses all rights to view catagory when exchanging through Interval).
We're quite pleased with the Penthouse purchase and the resort is really great. The extra dollar value is for you and only you to decide.