I've not had it but it is supposed to be about the same quality as Johnnie Walker Black.
From the JW website:
On the nose, Johnnie Walker® Swing is sweet and fragrant, and its initial light taste gives way to a rich, spicy and luxurious depth of flavor. Up to 35 whiskies are used in its creation. The majority of these come from Speyside, where single malts range from those matured for many years in sherry casks to gain richness, to others that are lighter and more aromatic. Swing uses a high proportion of these contrasting malts in the blend, complemented by malts from the northern Highlands and Islay to add spice and weight.
Swing was created in the 1920's and 1930's when luxury liners ferried high society passengers around the globe. With Prohibition still in force in America, transatlantic voyages represented the last chance to enjoy a glass or two of Scotch before disembarking at New York. One such traveler was Sir Alexander Walker, who noted that at least 2,500 bottles of Scotch Whisky were consumed during each transatlantic voyage. Thus in 1932 he created a blend suited to the style and elegance of this 'golden age' of travel.
Swing is bottled in a unique decanter designed to ride the ocean waves. Its name derives from the rocking motion of the bottle as it swings on a convex base when nudged. The design proved to be the ultimate solution to the problem barmen faced at sea as they desperately stowed loose bottles into racks to prevent breakage caused by the unrelenting pitch and roll of the ship.
Having already launched the world famous Johnnie Walker® Red Label® and Black Label® some 23 years earlier, Alexander Walker had little to prove, but he wasn't a man to rest on his laurels. Upon release, Swing was acclaimed as a masterpiece of blending and continues to be the Scotch of choice for international travelers. Currently, Johnnie Walker Swing is available only in Duty Free outlets.