I do love the SS hens!
My limited experience with SS roosters, about a dozen of them over a couple of years, from three hatcheries; about half were human aggressive, half were nice. I never had SQ or private breeder birds.
They are beautiful birds! I gave up plans to breed them, because of this problem. May you have better luck!
My SS roo is still quite young (17 weeks) but he's one of my favorites so far, out of a flock of 33 birds and 12 breeds!
He's very chatty, but not loud (not crowing yet). He's perfect with people - not friendly but never a problem.
He's an EXCELLENT forager (as is the SS pullet) and always gets the biggest bugs.
And I've never seen him be not nice to anyone - including the bigger rooster which we added to the flock about a month ago and who immediately became top bird.
I know this all doesn't mean much because he's so young... but I love my little Twig and thought I'd share my two cents