I loved to grow them and did so for a number of years. They are more of a novelty, I think, than anything, but I did like them mashed. They don't keep that deep color, they turn lighter blue (so does the water) and they have a faint "beet taste" about them. All that being said, I still think they are fun and looked great on my blue willow-like plates! A real entertaining difference from boring old white potatoes.
M