A very pretty apple the Rhode Island Greening is sour. SOUR! Like "sour green apples," like sugarless sour patch kids, like the best use for this apple would be vinegar.
To quote my sister "If anyone offers you a Greening, tell them NO." I didn't think it was quite that bad. It's not an eating apple for sure, though the Greening probably would be good for a cider blend if you ran out of crabapples.