The future Odo in "Children of Time" nearly perfected how to imitate a face, although it took a few generations to do so. Odo never really seemed all that interested in perfecting his shapeshifting skills. When he first met his people he seemed almost befuddled at the idea that they would spend hours in the form of rock for the sake of experiencing what its like to be a rock.
He can't do ears, but he can get all the feathers right on a Tarkelian hawk. Weird.