I spotted these in Fairway supermarket, on Long Island, this past weekend ($2.59 a pound). Didn't know anything about them, but they were such fresh, vibrant specimens that I figured I couldn't go very wrong. It peeled like a tangerine, felt tangerine-like in the mouth, but tasted like a lovely light, sweet orange. A Google search revealed that the Mineola is a cross between tangerines and grapefruits, but I didn't detect the grapefruit heritage.
Really delicious and very pretty. I'd love to see these more widely available.