John's an awesome guy. He has a great ability to consume technologies and present them in a clear and concise way.
These videos are professional and helped me quickly get up to speed with Angular (the greatest web framework yet).
John's videos are also featured on the Angular website.
PS - John also has the great pleasure of being a developer evangelist for Webstorm (the greatest web IDE) at Jetbrains.
PPS - You should follow him.