Combine sugar, water, butter and vinegar. Bring to a boil, stirring occasionally. Then, cook without stirring until a few drops form a firm ball when dropped into cold water (258°F). Remove from heat and add vanilla. Pour into a shallow greased pan or greased platter, and cool, turning the mixture toward the center with a spatula as edges firm. When cool enough to handle, slather butter on your hands, and pull taffy until light and firm. Stretch into a rope, and cut into pieces with scissors (dip scissors in water to prevent sticking). Wrap each piece in waxed paper.