I attended a workshop with both Eric Kim and Adam Marelli a few years back, and had a blast. I did learn some technical and formal things about composition and light, mostly from Adam Marelli, and I learned a whole lot about the social aspect of street photography and photographing and approaching strangers from Eric Kim.
Eric is fantastic with people. I've never met anyone who gets along with everyone in the streets in the way he does. He's just super skilled with people. And that's what I learnt from him. How to interact with people, and how to use photography to interact with people. This is just as, if not more important, than knowing photography itself...
In my opinion this workshop was one of my wisest purchases ever. Much more so than buying a new camera or lens or anything else that is material.
I also connected with a bunch of like-minded people from all over the world, who I stay in touch with. I visited one of the workshops attendees in Vancouver about 6 months ago and had a blast.
So... Did I learn a lot about photography itself? No. But I walked away with something far more valuable, and learned something far greater than just making pictures.