0e D&D has those little details...

Just lookin' at the Swords and Wizardry text, and I noticed that the ability score descriptions don't actually reference the "meaning" of the scores, only their mechanical effect. "Strength" does not measure your character's power, it "gives your character bonuses when attacking with a ... melee weapon." Very straightforward, almost jarringly so.
The best of these has got to be Wisdom:
Wisdom is the Prime Attribute for Cleric characters, and any character with a Wisdom score of 13 or higher gains a 5%
bonus to all experience point awards. If a Cleric has a
Wisdom score of 15 or greater, he gains an additional
first level spell.
Note the utter lack of reference to the fiction. Wisdom serves literally no other purpose than to, potentially, give you a bonus to experience and Cleric spell-casting. I cut my RPing teeth on much more complicated tables for ability scores - anyone else remember 18/01-00? If you rolled an 18, you got to roll on an additional chart to see what kind of 18 Strength you had - it's basically a minigame. That, and, who knows why, the 2nd edition design team decided to make 18 and 19 Strength very, very different values - they were preserving the might and majesty of rolling an 18, I guess?
Speaking of minigames - the whole 0e ability score thing is really six short games that give your character little party favors for winning - the physical stats grant bonuses that seem so triflin' that it draws the power of a good Int or Cha roll into question - you mean to tell me that +1hp/level is as much of an accomplishment (more or less) as knowing four languages? If you're a magic-user, the access to 7 out of 9 magic levels is pretty rad, too.
Maybe since every character has a score in all six abilities, they're just being granted a "suite" of different perks, a sort of grab bag with categories or something. I dunno.
Tomorrow I may sketch out some ideas for Level Three of The Lair of the Cyclops - it's technically the fourth area from the start of the dungeon, but I read a thing, and decided to hold off on Level Four encounters for now.

As it stands, the XP to be gained in these four areas gets you most of the way through the 3rd character level (jeeeeez, is that ever an overused term, with multiple, distinct meanings ^_^;;), unless of course you're a bad-ass Cleric with +15% XP - - Clerics already advance in level about 25% faster than Fighting Men, and 40% faster than Magic Users, so the extra bonus is just crazy - you can level up your Cleric twice(!) as fast as a Magic User if you rolled good Wisdom and Charisma (and the MU didn't). Is that why they're considered the most powerful class in the default S&W game? 'cause they get to access their higher-level content so much more quickly?
Honestly, I think it brings us back to being a polyglot (high Intelligence) vs. getting a single extra hit point every level - you have to claw and scrape for every little extra bit of help on dice rolling, but if you're clever you can possess advantages far beyond those of mere combat perks. Maybe? I don't know - it seems like Magic User is an "advanced" class - they rely the most on careful rationing of resources, but those resources can result most readily in "crazy shit happens" - consider how easily a lowly Hireling could reason out a mundane equivalent of a Fireball spell, and how hard it would be for a Magic User to reach the fifth level. So, you need to be super-careful with what you've got, but in exchange, you don't have to think as hard to get it to do what you want. Maybe?

It's late, and I'm trying to delve into the design ethos of the game. It's kind of interesting to ponder the role of "talking through" challenges - certainly, MU's have to think things through when it comes to combat situations, but they may have some spell on hand that's perfect for a puzzle or other non-combat encounter. The notion of being that careful both in and out of combat seems like a natural space for the Thief role to fill, but to properly do that, you'd need a character with very little explicit in-game resources of any sort. That would be a true "master class" for 0e - you literally have only your wits with which to win the day. (for that matter, the Fool archetype might very well make more sense here than that of the Thief, just to highlight the character's lack of special tricks or tools at hand)

This makes Clerics kind of the un-thinking-man's character - you have healing spells and attack-magic, you can turn undead, you can fight pretty well well... you've got it all!

It's pretty odd, in this light, that Thieves, who could be the aforementioned "master class", have so many weird little tricks in dungeon-crawl games (they do lots of damage with Backstab, they can circumvent drawn-out puzzles with Pick Lock and Disarm Trap...), and the nature OF some of those tricks seems to center around obscure or unusual situational rulings in-game:

"Well, instead of talking about tumblers clicking, or the shape of the key-head, let's just say that *your* dude can roll dice to open the door. Well, instead of pouring sand in a bag to get the idol's counterweight just right, let's just say your dude rolls dice to bypass the giant-boulder trap." This rambling thought-train stems largely from the enthusiastic suggestions of the "Quick Primer for Old School Gaming", most especially the "sixth Zen moment", that is to say,

This is a game about exploration, not combat.

Even when you're in combat, the point is to turn every possible, literally conceivable, advantage to your own ends, meaning that combat is just another puzzle. Your character's magical or martial powers act as a golf handicap or a buffer against having to use pure reason and description to get every little thing you want. This ties in to the "second Zen moment", or,

Player skill, not character abilities.

I was going to say that there is no [Forge alert!] "Conflict Resolution" in 0e, but that'd be incorrect - the conflicts you're tackling really are composed entirely of their component tasks. That's why you can't fudge *how* you do the thing you're doing; you get to fudge the How in games when the What (are you trying to accomplish) is more important. All we have here is the How - the game is all about encouraging and rewarding skillful players. On some level, the degree of seamlessness between What and How is pretty much complete, such that the rule book doesn't really cover anything else.
Hell, the bit about p.c. alignment is pretty sparse - to the point where they're basically saying, "Okay, this particular 0e game was actually published in the 21st century, long after other games had started using alignment. We don't really care one way or another, and there is absolutely no game effect for choosing whatever you want [for your p.c., that is. Protection from Evil is a 1st-level spell*]. But, hey, if the little bit of color it adds is important to you..." I have to respect the designers' complete apathy to the notion of Telling a Story, or The World Making Sense, in the face of Beating the Game.

*one last thing: I read the spell description, and it actually protects against "enchanted monsters", including both demons and the generally neutral-seeming elementals. Also curious: the Cleric can make this spell last for twice as long as the Magic User can. That feels like plain old niche protection; [Forge term] "Color" be damned!