Yes, I think this may be used for rootstock by some. Otherwise primarily an ornamental, as is Callery pear. Since the latter has also become a weed in eastern North America Ussurian pear may also have some pest potential. I haven't heard.

P.ussuriensis (Harbin pear) makes a good rootstock for Asian pear varieties - but I don't know which, if any, of the named varieties are reliably zone 4 hardy. I suspect most hardy european selections and hybrids would also be graft-compatible with P.u.

A great many cider apples are unpalatable as eating apples - has anyone tried making perry from Ussurian pears?

Rootstock and breeding. I think theyre also used for pollinating some pears as well (could only the the Ussurian hybrids). I have a "john" pear which is a hybrid with the russian pear. Nice looking trees and very very hardy. i have read conflicting reports of how the fruit tastes (for the hybrid).