My muscovy are sweet enough, but not always sweet to each other or my runners. The 2 muscovy girls that I currently have do not hang out together and do not get along. I have to pen and house them separately. I have 3 drakes currently, the youngest 2 came from the same nest and they get along well enough, but tussle quite a bit. There's no blood shed or anything so they are still hanging around. They always want to tussle with their father and he runs from them so usually theres no issue except they are housed separately as well.
My original 4 were hand raised and hand fed somewhat. My 2 youngest males were mama raised and I didn't hand feed because I didn't want to get attached as I had planned to rehome them. They will come close enough to me when food is involved, but they don't get too close which is fine by me. Since they aren't as tame, they are harder to care for if first aid is needed. But, I've figured out ways to do it.
The males seem more sociable than the females, but the females also are social (like they love to be the first in line of I'm digging in the dirt).
It works well for all of them when they can free range. But, this past year I've lost 3 ducks to a fox. So, they are penned more than they are out.
Muscovy hens are pretty broody. Mine go broody at least 3 times during the year. Multiply that by how many females you have, and it's a neverending circus of trying to break broody hens unless you want them to brood. They can brood quite a full nest - so if that's your intention, then it's a good breed. I took advantage of one broody duck and had her hatch out some polish eggs. My hatch rate wasn't good and the 2 survivors I had to brood in a brooder due to mama duck antics and the physical differences between ducklings and chicks.
Their eggs are rather large, so if you eat duck eggs that's a bonus. They are good at foraging and they are good at catching insects too.
Obviously they are pretty quiet compared to their mallard derived cousins.