Honestly, I resisted playing this game as long as I could.
I have a large extended family. I'm talking large here. I have seven siblings, roughly 50 cousins, and probably just as many second cousins, not to mention 9 nieces and nephews. Easily half of my siblings, and a third of my cousins, play Settlers of Catan. They started playing roughly five years ago, and they often invited us to come and learn to play, but we usually begged off. I'm sure part of it was because they all seemed so well versed in the game, and we were afraid of being badly outmatched. But we also heard the post-mortems, with one person being mad at another for being cut-off, or for playing a particularly nasty card against them.
We were finally roped into a game, a couple of years ago, under false pretenses (we were invited over for dinner, and afterwards, the Settlers boardgame appeared on the table) but have enjoyed the game ever since.
I mention this game, not to review it (there are lots of good Settlers sites on the web) but to discuss the applicability of its rules and mechanics to the OD&D endgame.
I mentioned levels of abstraction earlier. One of my frustrations with the D&D endgame is the lack of structure around stronghold and empire-building. Once you have "plunked" down your stronghold, it is assumed that you will derive a certain amount of resources from the hexes you control, regardless of the productivity, resources available, or populace. There is also little in the way of rules to govern upkeep of your empire, from building and maintaining roads, providing improvements and benefits to your subjects, maintaining your army, interacting with other empires, and so on. Some of these can happen at the micro level, I suppose. But part of the attraction of the endgame was to control kingdoms, direct armies, and oversee the macro operations.
One of the interesting things about Settlers of Catan is that it both recognizes that different kinds of resources come from different kinds of terrain, but also recognizes that some areas are more productive than others. It would be interesting to add those sorts of considerations to the OD&D endgame.