The Donahoes with the IVD coatings have only been out less than a year so it's really difficult to give a complete answer - only time in the real world will tell. They are only slightly different cosmetically then the regular coilovers - otherwise identical. The big difference is that with the coating you should still be able to adjust the coilover even after years of winters. There are examples of coilovers (Donahoe and others) of rusting to the point where the adjustable collars are totally seized, but I have not personally heard of or seen confirmed cases of any Donahoes IVD coated or non-coated coilovers becoming unusable or breaking due to rust.
Personally, I waited and waited until the IVD was released before getting my set. For my climate, the extra level of protection is simply required and worth the extra money. Just like buying some extra insurance on a vehicle you intend to keep.
Hope that helps.
Pete