The Collaborative International Dictionary of English v.0.48:

Surprising \Sur*pris"ing\, a.
   Exciting surprise; extraordinary; of a nature to excite
   wonder and astonishment; as, surprising bravery; a surprising
   escape from danger. -- Sur*pris"ing*ly, adv. --
   Sur*pris"ing*ness, n.
   [1913 Webster]

   Syn: Wonderful; extraordinary; unexpected; astonishing;
        striking.
        [1913 Webster] Surquedous

WordNet (r) 3.0 (2006):

surprisingness
    n 1: extraordinariness by virtue of being unexpected; "the
         unexpectedness of the warm welcome" [syn: unexpectedness,
         surprisingness] [ant: expectedness]