I gave this a try for about 3 weeks, my results (32y/o male)
Positives
-Hair felt softer overall
-I have sandy blonde hair, my hair tended to look darker
-Hair was easier to style
Negatives
-Scalp was more itchy, even though I rinsed very thoroughly
-Hair looked good but not as good as a light shampoo
-Took longer to rinse thoroughly than it did to shampoo
I went back to using an Argan Oil shampoo and just think my hair looks better overall. The rinsing in warm water actually seemed to dry out my hair than shampooing and quickly rinsing with luke warm water. I think those that have short hair will have better overall results. I don't have long hair but it is somewhere in the middle and it just didn't look very good without shampooing.
Also, if you're young, your hair is probably going to look pretty good shampoo or not. I'm very curious to see the results of older folks at ages when hair tends to start drying out a bit (30+ or so).