As with anything, judge it on an individual by individual and day by day basis.
I have reared turkeys and chickens and geese and guinea fowl together and it's not been consistent at all. In fact my experiences have been a caricature of how bad it can be. With time I made progress into breeding out many problem traits but as with chickens it’s far, far better to simply buy stock known for good behavior to begin with. Everything else is a waste of your time, I reckon.
First lot of turkeys with first lot of chickens: raised together since being little chicks. Went fine until one cockerel took to waiting until the turkey's backs were turned and then attacking them. Escalated from totally peaceful, having had them all grow up together, to having the whole lot of turkeys (male and female alike) chasing the cockerel to kill him. Culled the cockerel, for more reasons than just this incident, but the damage was done and the turkeys were thereafter always watching the other cockerels with a beady eye, and prone to attack any chicken.
Some males from this lot were friendly, others began to exhibit aggressive behavior if you turned your back. This was inherited from their fathers from the farm I bought them from. As a good rule of thumb, if you know an animal's attacked a human, don't buy its offspring. Wound up culling all this lot of turkeys for a bunch of reasons, after breeding them a few times.
Second lot of turkeys: mostly fine with chickens, until one male started trying to mate with chicken hens. Obvious issues there, especially since he liked bantams. Nearly killed some of my best hens, would have killed them if I hadn't come along at the right time. Also one tom turkey believed the geese were sitting on his girlfriend's eggs and attacked them to roll the eggs out from under them so he could sit on them. Caused losses of goslings. Also had to cull another rooster, who thought there was nothing more attractive than a displaying male turkey. He would slam himself into his tail whenever he spread it, and had the huge tom running scared. This rooster was hyperfertile, never seen anything like it, and I’ve also never seen so many terrible genes in one animal.
Most of the problems with this last group of turkeys were between themselves or with humans, not with chickens. The babies were super aggressive and would have screaming fights lasting until they were separated forcibly. This could drag on for hours. They would bite onto each other’s faces and not let go.
The female turkeys from both groups were never, ever content to nest in a cage, always exhibited a lot of distress no matter what I did and whenever in lay, they spent weeks whinging day in, day out, until let to do what they wanted, whereupon they whinged only slightly less. What they wanted to do was travel over several other properties to lay their eggs on the side of the road. When I say whinging, I mean repeating ‘weep-weep-wop-wop-wop’ loudly and NONSTOP. They were exasperating to say the least.
They had 75 acres to themselves but wandered even further afield, and generally never accepted whatever was on offer. The food, sure, but the rest of it, no. Even when kept without chickens they just would not be satisfied with anything. Again, from bad, very nervous stock; permanently overwrought and unhappy.
The turkey hens blamed me for any chick they lost to anything. Their gruges grew daily even when they weren’t losing chicks. Once bent, they never got unbent about anything.
They became very nest-aggressive and would later on become aggressive to chicken hens over nests, believing every egg they saw was their own. (Seems to be a common turkey delusion). I did for a while rear turkey babies under chicken hens and vice versa but both lots of mothers figured that out pretty quickly and abandoned every clutch that didn’t ‘peep’ right.
Turkey mothers tended to cause fatalities among their babies though, treading on them nonstop. They’d stroll around without watching where their babies were, and often stop whenever their strolling resulted on a foot landing on a chick, and then they’d just stand there, entire weight balanced on that one leg with a baby’s neck under their foot, staring off into the distance while it gasped and suffocated; if it was able to scream and did so, their response was invariably to make worried sounds in response while standing rock still on top of it.
If someone tried to shift them off the chick they would move in such a way as to render harm to it, so we had to just leave them crushing their own chicks if we let them rear them. Soon enough I bred towards better mothers but these ones, while watching their feet around their chicks, were all aggressive to humans. Cull, cull, cull…
In general the female turkeys were the most aggressive by far, and some ended up being permanently aggressive to everything and everyone. Even a female turkey can do a lot of harm if she attacks you.
I had also trouble with one aggressive mother turkey who would scratch the ground as a warning when a human approached --- in doing so she'd crush her chicks and destroy whole clutches. She had been a great mother before that, for many clutches. Again, multiple behavioral issues, culled them. Had problems with the geese and guinea fowl wanting to kill baby turkeys too. Got rid of them.
I bred multiple clutches from both lots of turkeys but one way or another culled the lot off. The tom turkeys can become troublemakers when the hens are brooding, either trying to mate with them while they're on eggs or chicks, or killing turkey chicks while trying to mate with them (which always happened out of the blue with males who'd previously been good fathers) and sometimes the toms would start attacking females rather than trying to mate with them, so I'd have to cull the toms. They'd mate normally up until their second year and then without warning switch to attacking whenever a female sat to indicate invitation to mate.
I also had severe issues with female-female aggression. One of my turkey hens killed another, and not one of the females was ever ok with the others for long. They hated each other, sisters or mother/daughter. The toms could get along with each other and roosters but were all cull worthy for one reason or another, sooner or later.
Here’s the kicker: all of the turkeys were fine to begin with. The hens got along, the toms got along, they got along with chickens, they were great mothers and fathers, they mated without problems, they didn’t do anything out of the ordinary --- until sooner or later they all just woke up one day and did something damaging. Every single turkey, in terms of behavior, started fine. The babies’ fights I’m not sure about but that level of aggression stopped when still young and was not represented in the adults, so that wasn’t an issue. They’d also been taking turns in sex-role-play ‘games’. I think that may have been related to a drought we went through for a while. The better natured turkeys I’ve had from these lots were all defective in one way or another and ended up culled or sold to be culled. While the first lot were raised with chickens, the second lot had their own cage and so forth rather than sharing.
Sometime in future I hope to try again because they were just bad stock, and not all turkeys are like this. I hope your experiences are better. Best wishes.
Lesson learnt. If I'd spent many generations on them I'm fairly sure I could have bred out the faulty traits, but I didn't have the set up for that. My advice when collecting turkey eggs is to not do it when they're watching you. A turkey mother is often very strongly emotionally attached to her eggs and babies, unlike a chicken mother. 
