This is an awesome build and I have been watching his motor evolve. The downside is that it is not only an outrunner but also a Halbach Array motor.
Nether of those are necessarily problems only that Halbach's are really difficult to construct. The magnets repel from each other as you have alternating magnetic fields. On the plus side a Halbach Array motor is much more efficient and you get "more bang for your buck" out of them but it is unlikely you will see them on mass production bikes on account of the cost of manufacturing.
The outrunner is an issue in of its self as you have a whirly spinny thing of death that if it explodes, and under stress it may well do (He hasn't tested the motor under duress) it is gonna make your leg look like Freddy Kruegers face.
I am looking at building my own motor for a bike, well... A Quadricycle so I could shield the motor behind the seat. The down side is all the maths it takes to calculate windings and magnetic flux. I have a sneaky suspicion he built the motor and calculated it's power off that. Something that won't do for an ebike with stringent laws regarding them in the EU.
