The Collaborative International Dictionary of English v.0.48:

Laudableness \Laud"a*ble*ness\ (l[add]d"[.a]*b'l*n[e^]s), n.
   The quality of being laudable; praiseworthiness;
   commendableness.
   [1913 Webster]

WordNet (r) 3.0 (2006):

laudableness
    n 1: the quality of being worthy of praise [syn:
         praiseworthiness, laudability, laudableness]