The Collaborative International Dictionary of English v.0.48:

Wonderful \Won"der*ful\, a.
   Adapted to excite wonder or admiration; surprising; strange;
   astonishing.
   [1913 Webster]

   Syn: Marvelous; amazing. See Marvelous.
        [1913 Webster] -- Won"der*ful*ly, adv. --
        Won"der*ful*ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

wonderfulness
    n 1: admirable excellence [syn: admirability, admirableness,
         wonderfulness]

Moby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "wonderfulness":
   awesomeness, beguilingness, enchantingness, enticingness,
   extraordinariness, fascination, glamorousness, marvelousness,
   miraculousness, mysteriousness, mystery, numinousness,
   phenomenalness, prodigiousness, remarkableness, seductiveness,
   stupendousness, wondrousness