Picked fresh, they taste almost wine-like. It's a very potent grape flavor. Adding the sugar for jelly really brings out the best in them. There's also a touch of a green taste (from the seeds, I guess) when you make the juice, but once it's made into jelly you don't notice it after that. I can see why people like to make wine from them too, but I would have to water it down quite a bit to drink it just as juice.
I was really surprised that the BBB didn't mention not to squeeze the juice bag. And I read about settling out the crystals online a couple years ago. I am an impatient person sometimes and I squeezed the tar out of it the first time I made grape jelly. That makes it very cloudy! My MIL told me not to touch it and she was right. You get beautiful, crystal clear jelly.
I liked it so well I put it in my avatar. Then I realized it was the exact same color as the hollyhock avatar I had before. I must just be drawn to that fabulous color! :rainbow-sun