When I first tried them, there was a little hiccup. The photos were underexposed by a stop or two on ettl. Then I turned them off and tried again. Everything worked fine. Had no problems since.
I recently got them. Used them once for a product shoot which I used a 430exII. I can control through the camera with ease: zoom the flash, exposure compensation, set to manual mode, change power output. Works fine, so far.
My yongnuo st-e2 didn't work with the 6d. Same problem with 5dIII which it would have sync problems. That is why I got the 622c.
Now I'm debating if I should just go 600rt down the road. Damn flash!