Probably one of the main reasons I ended up choosing ACKS as “my D&D” is the combat system: it strikes the perfect balance, for me, and the simplicity and quickness of the rules is a major part of that. I’ve got The Riddle of Steel and HarnMaster for when I feel like having realistic simulationist combat (TROS having the single best pre-modern hand-to-hand combat system there is in terms of realism, while still being among the most playable ones I know), but if you have a liking for D&D, that’s an itch that has to be scratched, and I find that doing it with simple rules is what works best.
… it certainly doesn’t hurt when you find a game that incorporates or makes unnecessary/extraneous all your houserules for AD&D.
I can’t help being interested in the split HD and HD-by-mass etc., but ultimately, for a D&D system, I was looking for something simpler than AD&D and something with more depth than BECM, and I got it.