Hmm.. Well. No, I have not witnessed excessive aggression. I have had buttons since February. Originally I had a male and 3 females in a smallish aviary. The male did chase the females every now and then, running around, puffing up and making a low, somewhat threatening noise. But it didn't take more than about 10 minutes for him to calm down and with 3 females in the cage it wasn't always the same one that was chased and they had room to get out of his way and hide. And he has proven to be a wonderful father, raising 21 chicks with his girls this year. Right now he and the 3 females live in a parrot cage as 12 of their (now grown) chicks live in the aviary. I have seen him being defensive about their food in the parrot cage, but I haven't seen him chase the girls in there.
I have 3 male chicks of theirs living together in a ~2x3 ft cage. One of those will peck at the others when food is involved, but other than that they seem fine together.
I also have 2 female chicks of theirs living in a ~1x2 ft cage. I have seen no aggression there.
The 12 chicks living in the aviary, are 6 females and 6 males, about 3 months old. I witnessed aggression in there for the first time a couple of days ago - a roo being defensive over food. I intend to remove the females from the aviary as soon as I have cages for all of them, to prevent the roos from fighting over them. Mating season is months away, I assume that's why they are still relatively fine together despite being both sexes in the cage.