I absolutely love my muscovy flock. I don't know if all lines are like this, but my line is totally child safe, they reproduce like crazy and try to get in three 20+ egg clutches every year with a great hatch rate, my favorite drake even cares for his own ducklings and leads them around the yard and sits on them (until they are old enough to realize he can be dominated, unfortunately, and then he's relieved when the males are gone), they're quiet, so friendly (except for nesting mamas-watch out!), they love foraging, they look you right in the eye and talk and dance to you, and when you finally do have to correct the male/female ratio to preserve peace and safety the meat is the best thing ever. But that's the bad part. For most of the year the best males are like puppy dogs and the girls are a riot-a little less friendly if they remember you as the egg stealer, but still party animals in their own right. The ladies honk when upset, trill when they're happy, and the drakes just HUFF and hiss. So funny. They're also amazing foragers and will empty your yard of snakes and other *surprises* for better or for worse (we had a lot of snakes, aka duck spaghetti).
As far as cons go, they are definitely seasonal eggers. Mine start laying as soon as it starts staying above freezing, then stop when freezing sets in again-not counting the times on nests, of course, but they eat so little feed while nesting I really don't mind.
They can FLY like eagles, and I'm talking over your house, not just over the fence, and they LIKE it, so you either have to pinion in the first week (not hard or traumatic surprisingly), or watch carefully for molts and do your yearly duck rodeo to make sure your birds don't get lost or hit by cars if that's the kind of area you live in. I've discovered it's a lot harder to ride your drakes and clip those huge wings while they try scratch you off with all they've got-and they're pretty big and strong. And heads up, pinioned birds can still fly about four or five feet high, but like I said, you won't see them winging it to the next county, just the occasional escape from the pen.
The feathers when processing do not want to come out if you do them too late. Scalding and duck wax will become mandatory if you procrastinate like I did this year (shame on me, but I think most people can understand).
Those girls are wired to make clutches, feather their nests, and SIT...for 38 days. As soon as the spring season starts they become single minded, but even that's not terrible as long as you can handle it. And the worst mine do is pinch when you go under them. Just watch out for that nasty, cement colored broody poo. Never upset a sitting muscovy hen or she may foul her nest and you.
The worst part is their massive claws. They are flying, perching ducks. Their talons are sized accordingly. They WILL try to scratch their way out of trouble, and if you don't know what you're doing, wear a big thick coat and gloves for the first year whenever you have to handle them because they WILL scratch you deep, and it WILL get infected. I'm to the point now I don't usually get scratched unless I do something stupid (hey, female ducks don't like to be absent mindedly patted on their fluffy underpuffs like a football-totally my fault), so I usually don't anymore, but DANG those claws. Babies have sharp little scratchers too. Luckily once they get big, at least if you've clipped their wings or have them pinioned, you really don't have to handle them often. All you have to do is herd them and it's all great.
All in all they are great birds. I love them, and I hope to never be without them again (unless, of course I couldn't let them reproduce, then that wouldn't be fair to the girls who become hatch machines every spring, but re-become themselves each winter).