I've bought the bimonthly Explorer subscription for my dad for Christmas for the last few years, and he really enjoys it. It's allowed him to try a lot of whiskeys he might not otherwise purchase, and the customer service has been really great on the few occasions we've had shipping snafus or they've been out of town. As a whiskey drinker myself, on the occasions I've been able to join him for a tipple, they were quite good.
From my dad himself: "I like the variety. It is one of my favorite gifts. A fun surprise every couple of months."