Positives of Bony
She will clean the house, do repairs, sometimes chase down the burglar, rake leaves in the fall if you have SN.
Negatives: She won't leave babies and toddlers alone, constantly waking them up from their sleep. If a meal is cooked she will put it in the fridge when the family is coming to get a plate. If you have a party she will get the cake and put it up. The guests are then upset they didn't get a slice. She will go and rake leaves, which is good, but she will ignore the house cleaning unless you tell dismiss her, give it a couple of minutes and then awaken her.
If you have a bar she will make a drink, pee on the floor, mop it up. Make a drink, pee on the floor and mop it up; make a drink, pee on the floor and mop it up. . .
I gave up having a bar. Unless you can put it in a room and lock the door to keep her out, it isn't worth the hassle, but that depends on how important a bar is to you.
The negatives seem to out-weight the positives, but that is dependent on how much you want your sims to spend cleaning the house and doing repairs. With a family of six, it can gets dirty quick and I find her more than worth the problems. I just put her in a room and remove the door or build a box around her and leave her there until the babies age up to child.
She doesn't feed babies, change diapers or cook meals normally. That doesn't mean she won't on rare occasions, but they are rare. Extremely rare. I have had the same Boney in a family that is now at the fourth generation and she has cooked a meal one time.
There is a thread somewhere that is about Boney, you could do a search for it, I'm seem to have trouble getting links to work or I would make one.
I can't imagine playing a game without Boney, but some don't feel she is worth the problems. To each their own.