I don't know about "special", but they play really well for me. Stiff but still gives good feel/feedback. Lower deflection than standard maple shafts though not as low as carbon fiber which I've never liked.What does the Hsu shaft do that is so special?
I had my last one built to fit a specific butt and it was perfect.
They just work really well for me, and to my eye look great too.
Of course ymmv...