I have a pair of 6-month-old Svarthöna and I quite like having them around. They're very docile and easily tamed, in fact, they're annoyingly friendly at times. They are a smaller bird, so their eggs aren't full size, but that's just a minor inconvenience.
My Svart Hona are among my favorite birds. They always come over to interact or see what's happening when I go to the coop/run and neither the hens or roosters have shown anything but the best behavior. My SH rooster is my dominant flock rooster and is easy when mating the girls. He's in a coop with 14 pullets and another rooster (barred rock bantam) and they get along fine - both crow, both mate the hens, etc.
I hatched a few just to add to my flock and all ready planning on expanding in the spring and eventually moving them to their own breeding pen (along with some hobby project crosses). I can't recommend them enough - the only down side is that their production isn't great, but I knew that going in.
Pros - Memorizingly beautiful, calm, hardy, friendly, good foragers, good flyers, play well with other breeds
Cons - Too small to be a good dual-purpose breed, historically hard to aquire, a little shy, the bottom of the pecking order in my mixed flock
Very happy with my Svarthona. They are great birds. Healthy and even tempered, if not a little shy. Good with my kids. Absolutely gorgeous. A hit with friends and family (even "non-chicken people"). As someone that raises birds for eggs and meat, my only wish would be that they were a little larger.