I was at a low key 5k on labor day in my hometime and I was surprised to see how many people forked over the $250 for amateur glory. Did it help with their performance? Hard to tell. A few people wearing them ran great, but then the rest ran their usual 5k result. I tend to agree with Amy Cragg's comments regarding the biggest advantage of the Vaporfly 4%/Next%. To paraphrase Amy, she felt that the Vaporfly's didn't beat up her legs as much as a typical racing flat/light weight trainer. Therefore, she could recover faster between sessions.
I find the Vaporfly obsession quite interesting. From a general scientific perspective I believe that the material properties of the Pebax foam provides the biggest advantage. Nike found a material that has an optimum density, weight, energy return and durability. The other shoe companies are trying to catch up and find a Pebax like material to feature with their premium marathon shoe. IMO-the competition between shoe companies that the Vaporfly has started will benefit the everyday runner. When Addidas/Skechers/Sacuony/NB come out with their premium marathon racers at a more competitive price we all win.
I do have to admit that it is a good feeling to stride past your Vaporfly strapped competition in the later stages of a race in your standard/racing flat or trainer.