The sweater coat is a great winter staple for any shape or size. It looks great layered over a tank with jeans and boots or added over a LBD with tall boots or flats. This is my wardrobe item of choice for the Christmas day family visits. It's warm and comfortable but not shapeless and unflattering.
A word of caution on the sweater coats, please make sure to get one that is either belted or more structured. (think sweater blazer or something that hangs straight down with not a lot of extra fabric in the front...that adds weight)
PS: Both of my sweater coats came from Old Navy and I LOVE them.