I'm a subscriber and I'm enjoying it very much. I really like hearing Monte talk about "why" he chose to do things in a particular way.
I intend for the dungeon to become a fixture in my next campaign (set in Ptolus). I see it being a great resource.
I subscribed to one "patron dungeon" and got bored halfway through the process because I felt that once it veered away from what I was interested in, I was ignored. (Not unkindly, nobody was rude, but the adventure just didn't go the way I wanted it to, so I got tired of it). DaD so far has been exactly what I like and want in a dungeon.
And the forums are fairly active. I'm enjoying them, too. I'd suggest that its my replacement for Dungeon magazine, which since I don't play 4e, no longer suits me.