BH used to have Welsh Blacks years ago, and still had one when I first came here.
He was loathe to give an opinion, saying that it's been such a long time since he had them, they could have changed since then.
One thing he says you used to have to watch out for was 'big teats' - they'd develop such large teats the little calves couldn't get their mouths around them. (Swaledale ewes get a similar thing. You have to catch them and set the lambs on, sometimes you have to milk some off for the first few days to get the teat to be less engorged.)
Hopefully they'll have bred that problem out of them by now.
When he used to have them they were quiet, hardy, milky, good mothers, long-lived. Hopefully none of that has been bred out of them!