Are these varieties really that cold hardy?
Yes! These are some of the most cold hardy varieties in the world. They’ve all borne a full crop after temperatures of -30°F or colder. We don’t like to give a precise value for exactly how hardy they are because there are so many variables involved. For example, overcropping or poor disease control the previous year will substantially reduce the hardiness of any grapevine. Even when well grown, every winter is different in terms of snow cover and acclimation (or deacclimation) conditions.
Is the wine from these varieties actually good quality or is it just acceptable where few other grapes can be grown?
These varieties really can make excellent wines when well grown and vinified. Proof of that are the numerous medals wineries in Minnesota and elsewhere have been winning in national and international competitions with these new varieties. They are also now starting to be planted in mainstream eastern wine regions where growers have many other options to choose from.