During my recent visit to Copper and Oak in NYC, I started the night with the rum finished Blood Oath Pact 5.  The wife was at my side, sampling rums.  I decided to keep the rum theme alive by selecting the Glenfiddich 21 Reserva Rum Cask for my second pour.  Rum is my second favorite spirit, so rum finished whiskies usually pique my interest.  Unfortunately, I too often find that rum finishes don't add a lot - perhaps some general sweetness, but not much else in terms of additional notes, depth, or complexity.   Not so with this Glenfiddich.  Short of blending in copious amounts of actual rum, I'm not sure the rum notes could have been any more prominent - tropical fruit and brown sugar most notably.    Not to be outdone, the underlying whisky is also quite bold, with a typical Glenfiddich profile, but more dry and somewhat bitter on the finish.  It veered towards unappealing.  But the biggest shortfall is a lack of integration between the malt whisky and the rum notes.  It comes across as a forced marriage.   This is a complex whiskey that has inspired a very wide range of opinions in the reviews here.  Despite my initial misgivings, I'd be interested in trying it on multiple occasions to see if my reaction varied.  But due to the price, that's not going to happen.  At well over $100, it's far outside of my "this could possibly get better" range. I feel like this whiskey should be a part of Glenfiddich's Experimental Series, even if it's an experiment that didn't quite work (I do usually like Glenfiddich's experimental efforts; the Fire & Cane and XX are both winners).  With a price tag aligned to the rest of the Experimental Series ($40-70), I'd be a lot more forgiving.