I never was a fan of the first generation Valkyries myself but the other day I was riding a Goldwing that's in my shop for fork seals/bushings. I didn't realize how radically different it is than the Valkyrie weight wise. You can really throw the Valkyrie around compared to the Wing.
I've never been a fan of car tires on bikes myself mostly for cosmetic reasons. With my riding style (mostly touring, not twisty riding) I imagine it would "do the job." I've honestly never seen any definitive tests or data that show how different they are than a traditional motorcycle tire. I'd be interested in seeing a real test between the two. Personally I've always thought of motorcycles as "luxury items" so buying motorcycle tires every year or so didn't bother me. Although I am a "soldier of fortune" so if I saw proof that a car tire out performed a motorcycle tire then I'd switch. It wouldn't make sense not to.
I think the word "functional" and "better" often get confused in this argument. Does it work? Technically yes, as we know many people who do it. Is it better? Economically for sure since car tires last far longer than motorcycle tires, but I haven't seen any data to prove if it performs better (I also haven't looked since I've never actually considered switching myself).