I am sorry that your post got so few reactions. I think this is a very interesting plant, that I might be growing some day. I did not reply because I have no experience yet, but I did find some interesting on the internet that I would like to share with you since nobody reported this from actual experience. It was mainly on Dutch and Belgium sites. I would send a link, but you might have some trouble reading it.
This plant is so interesting because it is a natural protection against certains potato pests. The roots attract parisites that harm potatoes (Globodera pallida en G. rostochiensis), but they find nothing to feed of and die. Therefore it would be useful to plant them in combination with potatoes or before potatoes.
The reports on the taste varies per site: some call it "the most delicious thing ever eaten" and other "awful taste" The latter do plant it because of the benefits in combination with tomatoes.
Your request on winter hardiness: The plant perenial, but not fully hardy, but it makes rhizomes that might survive the winter if your freezing is not to deep (maybe some cover might help?). In the Netherlands they do stand a change and they appear in the "wild" as well.
The downsides of this plant are nasty thorns; so don't plant them near a path and wear gloves during harvest. The rhizomes might result in some invasiveness in your garden as well. If it is tasty it might balance with the thorns. Maybe somebody on permies can breed out the thorns?