Yes, I used a whole can of concentrate, however I had already drank about 6 pints out of the keg before adding. I've seen recommendations of anywhere between 1 & 3 cans to sweeten. I like the flavor of the cider however I was hoping for something just a little sweeter. My gravity readings went from 1.063 to 1.012 so there wasn't a whole lot of sweetness left.
I'll let you know if one can changed it much after I sample it tonight.