Pros: Good mothers, free range well, friendly nature
Cons: Not the best egg layers
I have 2 Dark Cornish hens in my free range flock and they are easily my favorite. Both are friendly towards humans. The main downside, as i see it, is that they go broody a lot. By a lot i mean my girls hatch babies out 2-3 times per year in all sorts of weather. For that reason i think it's a good idea to have a couple dark cornish hens if most of your flock consists of non broody breeds. That being said, if your only goal is egg production, having a flock of nothing but dark cornish would probably be a disaster. Their mediocre egg production combined with a high frequency of broodiness, would make them less than ideal for that purpose.