Just to offer a dissenting opinion on cask strength Scotch, I find many of them quite worthy: Laphroaig CS, Ardbeg Uigeadail, the aforementioned A'bunadh, and many of the Gordon & Macphail single-cask bottlings.
That said, the argument could be made that the lack of chill filtration and the added strength and variety of ages (not including the G&M) in these bottlings add dimension to otherwise less nuanced whisky: either peat bombs or sherry bombs. I can't disagree much, except to say that a cask-strength Dallas Dhu I sampled once was mind-blowing (and other G&M efforts, too), to say that I find Ardbeg and Laphroaig quite complex even at their standard strengths, and to say that cask strength bottlings do afford the luxury of adapting a particular flavor profile to fit your own palate more readily than do already-diluted iterations.
All of the above being said, I wonder if slightly lower barrel entry proofs among Scotch producers account for some of the "difficulty" inherent in enjoying cask-strength Scotch. I have rarely seen a cask-strength Scotch go over 115 proof, while barrel-proof bourbon exceeds 125 proof regularly. Stagg, Booker's, etc., seem to benefit greatly from water being added, while 100-114 proof bourbon fares well. Scotch with comparable percentages of dilution, rather than comparable proofs, might be a more fair comparison.
Throw all of the above out the window, natch, when tasting barrel proof rye. To wit: Handy rye (2007 batch) is the finest whisk(e)y from anywhere in the world I've tasted. It suits my palate and my "objective" definition of good whisk(e)y, too.
All of this brings to mind what may be an obvious question: where is the barrel-proof Irish whiskey? Can you imagine how rich and multi-dimensional Redbreast 12 would be at cask-strength, given its already mouthfilling, fruity depth?