The reality is running with VaporFly DON'T make you run faster.
It's merely saves your legs to recover faster.
Athletes are just as likely to get injured or burn out from training/running with VaporFly as they do with traditional running shoes. Case in point : Check all the elite athletes training/racing with them. The track record speaks for itself.
It's merely a placebo effect.
Even if it's indeed 4% improved in efficiency (that Nike promises), it doesn't mean it translates into 4% improvement in times.
I've run in VaporFly in dry runs and it doesn't feel like you run any fast at the same effort and heart rate. This can be confirmed by many objective tests. Go ahead, put a power meter on it or run a workout with it without the use of a watch. See how it performs. You won't see any difference in performance.
Yes, it feels different from other shoes, but lots of shoes feel different from other shoes. It doesn't mean it's better.
It's really a millions of dollars Nike marketing arm telling you it's better, nothing more.