The Collaborative International Dictionary of English v.0.48:

Virtuosity \Vir`tu*os"i*ty\, n.
   1. The quality or state of being a virtuoso; in a bad sense,
      the character of one in whom mere artistic feeling or
      aesthetic cultivation takes the place of religious
      character; sentimentalism.
      [1913 Webster]

            This famous passage . . . over which the virtuosity
            of modern times, rejoicing in evil, has hung so
            fondly.                               --C. Kingsley.
      [1913 Webster]

   2. Virtuosos, collectively. --Carlyle.
      [1913 Webster]

   3. An art or study affected by virtuosos.
      [1913 Webster]

WordNet (r) 3.0 (2006):

virtuosity
    n 1: technical skill or fluency or style exhibited by a virtuoso

Moby Thesaurus II by Grady Ward, 1.0:

118 Moby Thesaurus words for "virtuosity":
   ability, accomplishment, address, adeptness, adroitness,
   aesthetics, airmanship, artfulness, artisanship, artistic taste,
   artistry, ascendancy, bravura, brilliance, capability, capacity,
   cleverness, command, competence, connoisseurship, control,
   coordination, craft, craftsmanship, cunning, dash, deanship,
   deftness, dexterity, dexterousness, dextrousness, dilettantism,
   diplomacy, ear for music, eclat, efficiency, elan, epicureanism,
   epicurism, excellence, expertise, expertism, facility, favor,
   finesse, flair, friandise, gastronomy, grace, greatness, grip,
   handiness, horsemanship, incomparability, ingeniousness, ingenuity,
   inimitability, know-how, lead, majority, marksmanship, mastership,
   mastery, musical ear, musical sense, musical talent, musicality,
   musicianship, one-upmanship, panache, perfect pitch,
   practical ability, precedence, predominance, predomination,
   preeminence, preponderance, prepotence, prepotency, prerogative,
   prestige, priority, privilege, proficiency, prowess, pyrotechnics,
   quickness, readiness, relative pitch, resource, resourcefulness,
   right-of-way, savoir-faire, savvy, seamanship, seniority,
   sense of rhythm, show, showmanship, skill, skillfulness, staginess,
   style, success, superiority, tact, tactfulness,
   technical brilliance, technical mastery, technical skill,
   technique, timing, transcendence, transcendency, virtu, wit,
   wizardry, workmanship