I love sweater dresses. They are so easy to wear, comfortable, and cozy, yet you look pulled together since you're wearing a dress.
For added warmth, add tights or leggings. Maybe even super skinny jeans, if the dress is shorter? That might depend on how smooth the jeans look underneath - you don't want the belt loops to be bulging out under the dress.
To make this a bit nicer looking, I could just add jewelry and a cute bag.