My appreciation of the First Fantasy Campaign (my review in Part 1, Part 2, Part 3, and Part 4) didn't really strike until a decade after I bought it. While I like the "window" it opened on the early days, as practical product it left a lot to be desired. But then after a few years of GMing I found myself with same collection of jumbled notes for the Majestic Wilderlands. They meander through different topics, most incomplete and sadly holes from lost fragments. After that realization I appreciated the First Fantasy Campaign a lot more.
The First Fantasy Campaign illustrates a theory of mine about why most of the classic dungeons were never published. If you look at the Blackmoor dungeons they appear little more than a sketch with a map. The key to how it worked is in the section on magical protection points which looked to be used by Dave and his co-DMs to "stock" levels. Only a few rooms were actually highlighted in detail. It appears to me that what happened was that as players roamed the map the referee making up the details with help from tables or "Magic Protection Point" guidelines. So Blackmoor is much fuller than it appears in First Fantasy Campaign.
Probably the clearest example of this style is the original Tegal Manor. You simply can't run that module without reading the notes on the map about the various rooms. If you try to run it with just what in the book the result is somewhat bland.
The module as we know it , came out of the need to run AD&D tournaments at conventions. If you look nearly all the oldest modules originated as tournament modules. They also had the advantage of being readily publishable as they already were formatted to be distributed among dozens of referees.
Because of this the layout of tournament modules became the style for nearly all published modules. Keyed maps with all the keys fleshed out in the text by the standards of that RPG. Today that philosophy has led to the encounter style format for 4th edition.
The advantages of the format of Tegal and Blackmoor is that the referee has a lot more creative freedom to interpret the dungeon while still saving him prep time. It is a more compact format which means in theory it can be as expansive as the AEG's World's Largest Dungeon but not be the World's Largest RPG Product. Replay value would be higher as referee rework the rooms after the PC clear them out.
Thinking about this causes me to wonder if the tournament style is the only format the modules could have taken. Certainly the presentation of Tegal Manor and the Blackmoor dungeon leave a lot to desired. But I think it could be vastly improved yet not lose it advantages. When I wrote Points of Light s I had improvements I wanted to add to the Wilderlands format to make more usable to the modern referee. Perhaps the same can be done for the module as well. I think this can cut across editions and apply equally well to OD&D, 1st, 2nd, 3rd, or 4th.