The Collaborative International Dictionary of English v.0.48:

Disagreeableness \Dis`a*gree"a*ble*ness\, n.
   The state or quality of being; disagreeable; unpleasantness.
   [1913 Webster]

WordNet (r) 3.0 (2006):

disagreeableness
    n 1: the quality of being disagreeable and unpleasant [ant:
         agreeableness, amenity]
    2: an ill-tempered and offensive disposition [ant:
       agreeability, agreeableness]

Moby Thesaurus II by Grady Ward, 1.0:

25 Moby Thesaurus words for "disagreeableness":
   disagreeability, displeasingness, displeasure, distastefulness,
   inhospitableness, inhospitality, ugliness, unamiability,
   unappealingness, unattractiveness, unbenignity, unbenignness,
   uncompassionateness, uncordiality, undelectability, undesirability,
   ungeniality, ungraciousness, unkindliness, unkindness,
   unpalatability, unpleasantness, unpleasingness, unsavoriness,
   unsympatheticness