Assuming you aren’t weirded out by the artwork then LotFP shines as pretty much the tightest version of D&D ever. This virtue comes across most clearly in the section devoted to what I call “operations”, i.e. how to open a door or check for traps or crap like that. Most reviews of most D&D descendants (and many whole games!) completely skip this stuff because it's usually boring to read, but in actual dungeoneering play these mechanics are crucial. LotFP delivers the best, most coherent set of operations rules I’ve ever seen.
Let’s consider all the rules in D&D that don’t have to do with combat or magic. Let’s call these the “operational rules”. (Which may be slightly different than what Jeff is talking about above. This is my springboarding off his post.) There’s a surprising amount of them. Even in ye olde original D&D. They are often glossed over when talking about the game, but I’ve come to see them as very important.
These operational rules are what makes D&D an exploration game rather than a combat game.
Take a look at the combat system. Excluding Chainmail and WotC D&D, the D&D combat system is enemic compared to wargames of the era. (Oh, let’s exclude AD&D too just to keep it simple.) And D&D was created by wargamers. That says to me that D&D wasn’t primarily about combat.
Of course, there’s also the fact that D&D is a role-playing game, and that role-playing doesn’t really show up in rules. Yeah, I know you might disagree with me, but whenever I see rules that claim to govern role-playing, I generally see just another mechanical game rather than role-playing. Role-playing happens in the spaces between the mechanics.