SmootLookAtC.cs

using UnityEngine;
using System.Collections;

public class SmootLookAtC : MonoBehaviour {

	public Transform target;
	public float damping = 6.0f;
	public bool smooth = true;

	// Use this for initialization
	void Start () {
	
	}
	
	// Update is called once per frame
	void LateUpdate () {
		if (target) {
			if (smooth)
			{
				// Look at and dampen the rotation
				var rotation = Quaternion.LookRotation(target.position - transform.position);
				transform.rotation = Quaternion.Slerp(transform.rotation, rotation, Time.deltaTime * damping);
			}
			else
			{
				// Just lookat
				transform.LookAt(target);
			}
		}
	}
}