"Is there really any fundamental difference between your right angle nymphing set up and just running a mono leader off the flyline? That is, how real do you think the right angle is compared to a leader from the end of the line to an indicator and thence to the fly?"

I use a customized corkie to 'right angle' fishing sometimes. Does it make a difference? Depends. The other day I was fishing egg patterns - tiny eggs, very little weight. I was fishing in slack water and on the inside\soft edge of the seam line. You could clearly see the egg 'flies' hanging direcly below the 'indicator'. I could quickly adjust for depth and have confidence that I was in the zone - even when I cast out past where I could actually view the flies. You still have to mend the line as you would when float and jig fishing, but the mending did little to raise the fly out of the zone.

As I began working faster water, the confidence of the depth the flies diminished. In that instace, I took off my indicator and added some split shot to just roll the eggs along the bottom - using line mending techniques to keep the flies down deep.