I am a subscriber - can't say whether or not it's doing well but there are definitely lots of people on the subscriber-only forums.
For me the design stuff is intriguing, and I'm not sure if I will or won't run the mammoth dungeon, but it's absolutely worth it in terms of just rooms and encounters that I can rip out and put into my own stuff. In addition, to further describe myself as part of a niche of a niche of a niche, I am a 3.5/OGL player AND I own a whole slew of Dwarven Forge pieces...each room in DaD is depicted as a standard map, and also as it would look made from DF pieces, so I can recreate any of them.
It's not all dungeon crawls, either, though that is certainly the main bit - any group that can't find ways to RP in ANY scenario has issues IMO.
I would say that anyone who paid for adventures that they cannabalized by subscribing to the old Dungeon magazine would love this stuff.