I like Blackmoor.
Like the old setting, like the new books.
Haven't used it directly though because of the fact that I have my own setting. But it was to me very influential, as a game setting, in devising elements of my own fantasy world (Ghantik). there is even a particular region and "dungeon" in Ghantik based on certain adventures from Blackmoor.
What I like best about it is the fact that it is small and compact (as a world setting), relatively speaking, and yet "filled." It is brimmed-over. I like the way magic works there, and the openness and looseness with which things can operate.
It is also both heavily realistic, compared to later games and settings and heavily mythological, but in a yeoman's or working man's way. It is direct and gritty to me.
I recommend it, if nothing more than as inspiration, but if you don't have a setting, then it's a damn good one. It's old school, gritty, fascinating, and dark.