"Darker" than I had expected - and better! Nicely leather-y and rich, with the higher ABV providing lift and power without turning things too boozy. There's a pleasant sense of Bourbon/Sherry-interplay on the nose, without one side getting the upper hand. The typical Glenfiddich fruits and florals are there, but the casks definitely have had their say. Water makes the nose more buttery and soft and lightens it up a bit (tending more towards Bourbon-cask aromas now). Gets more oaky / older-seeming with more time in the glass.
Without water, it's perhaps a bit tart and acrid in the mouth, almost as if we're tasting Arran. Very good though, with a strong and sweet body and (for Glenfiddich) almost an oily mouthfeel. Reduced, things get more approachable, though the tart edge remains. So what flavors do we get? I'd say oranges and pears (with the peel), salted caramel, and some interestingly chalky/mineralic associations, somewhere between aspirin tablets and limestone. Good stuff!
The finish is medium, with some subdued sweetness and lemon sherbet lingering the longest.
Overall, a really substantial version of Glenfiddich at a great value-for-money ratio. A sleeper candidate for my very own private bang-for-your-buck award...