Uniformity. In the Dungeon Masters Guide (p. 7), Gary states, "Dictums are given for the sake of the game only, for if ADVANCED DUNGEONS & DRAGONS is to survive and grow, it must have some degree of uniformity, a familiarity of method and procedure from campaign to campaign within the whole." In my opinion that's part of the problem with the OSR movement. Everybody seems to want to come out with their version ("vision") of the old rulesets. If Labyrinth Lord is adequate, what need is there for Swords and Wizardry, Complete, Whitebox or other? If B/X Companion rounds off Moldvey, why even bother with Dark Dungeons (yes, I know, DD is a BECMI emulator)? Or, ultimately, with so many copies of the original rules on Ebay or even pdfs (mostly pirated, admittedly) why even bother with "clones" at all?
This is not to disparage any of the "clones." It is clear that the authors all have an excellent grasp of the system and the material. But they're all slightly different and not ~exactly~ compatible. As Gary goes on to say on the same page, "ADVANCED D&D is more than a framework around which individual DMs construct their respective milieux, it is above all a set of boundaries for all of the 'worlds' devised by referees everywhere. These boundaries are broad and spacious, and there are numerous areas where they are so vague and amorphous as to make them nearly nonexistent, but they are there nonetheless."
I probably worry for nothing, but I am concerned that the movement will subdivide into a group of mutually antagonist people. Feel free to prove me wrong.
AC: 2  Special: Confusion
HD: 8+8 Move: 6/1-6 (when burrowing)
Attacks: Claws, bite HDE/XP: 9/1100
Despite their lumbering, beetle-like appearance, Umber Hulks are actually an intelligent subterranean race that culls ankhegs, cave fishers, hook horrors, young purple worms, and the like for food. Their exoskeleton protects them better than plate armor and their large mandibles can cut through armor for 2d6 damage. Anyone who meets the gaze of the Umber Hulk must save or become confused for 2d6 melee rounds.