I'm like you and always fishing upstream in the belief that I am behind the fish. However more and more people (and ones who really know what they are doing) seem now to be going for the downstream approach with nymphing. I do not really know the specific rationales but can say that it is done in all water conditions and not a selection of circumstances. Something tells me it is a variation on Czek nymphing??? I noticed a guy recently doing this in a very fast flowing stream, and he was doing better than I.