I got 10 guineas this year as companions to the flock. BAH! I wish I had just gotten a bunch more chickens. I swear they share a brain between them. I keep my chickens in a fenced in area and I wanted the guineas to fly around and forage and then fly back over the fence to go to bed with the Jersey Giants I have. Well, they fly over all right (at least some of the 10 fly over) and then they can't figure out how to fly back. They just pace back and forth along the fence keeping the remaining guineas in sight. I have yet to get the stupid things to fly back over at night and they are 4 months old now.
Now, I don't have a problem with my guineas beating up my chickens because I have whopping large Jerseys and I think the hens established a pecking order when the guineas were keets. If you have smaller chickens they might have issues. I don't know.
BUT.. guineas are funny creatures. Entertaining. That's about it. If I ate meat at all they would already be in sauce.