I like a lot of OSR games, love a few, and others I can't describe my feelings for. I generally hate Retroclones. Retroclones are strictly letter rather than spirit of the rules translations of games. For a long time I hated Labyrinth Lord because of it being B/X. Well apparently it's not B/X. OSE is B/X. And while I still hate LL because where it is designed it is designed poorly, OSE knew not to fuck with the formula and shows that B/X is better than Labyrinth Lord. Here's a few reasons.
One that nobody in the fucking earth will believe or easily understand: Classes are balanced in OSE. This was hardcore-dyed-in-the-wool-fucking-wargamers-stress-testing-balance flavor of balance. Better than anything we've seen out of WotC, better than TSR later on, better than most of OSR. A few notes that other OSRs can learn from:
Like OD&D, it's baked in that you dump str, int, and wis for whichever stat is actually important to the character. You are mechanically likely to have at least one of these stats high, and you can burn it 2 for 1 to add to your prime requisite. This fits together like a solid machine, and it's so innocuous that nobody even fucking talks about it. That's why it's my first bullet point of the system - the game accounted for random chargen. The best part is some stats can't be modified, so if you're inherently charming or tough, you can't sacrifice it. This even has story implications. If you were smart and decided to be a thief, you spent time honing your reflexes and neck hairs instead of reading, so your brains went on the wayside. There's no real easy way to train away speed, stamina, or commanding presence, so those are off limits. This mechanic says a lot without really saying anything.
Clerics don't get spells at first level. The class actually has a false level up at second level. The reason the class has always had the second to lowest XP progression is because it doesn't get full functionality until level 2. This is important because getting to level 3 requires more XP than any class getting to level 2. Like the Thief, the Cleric is supposed to be running about one level ahead of the party.
Thieves are maligned in the system for being "weak". But really they are only weak at level 1, like Clerics, and they almost always run at one-two levels above the rest of the party. Meaning they have up to 2 HD more than the rest of the party. So it only makes sense to give them a d4 HD. Most gamers have trouble looking at the big picture, so they want to give the Thief d6 HD or Clerics spells at level 1 and don't understand that level 1 for each class is the trial run for whether you can really play that class. Lastly Dex is their prime requisite and they are unique in this. They can burn one-third of their stats to make their Dex higher. Dex has always been the best stat in D&D, and the game understands this and uses it to make the Thief balanced.
Fighters are maligned for being without any real mechanical doo-dads to play with. Their chief benefit is burning useless brains stats for Strength, which gives them a bonus to everything they really want a bonus for. Plus they are the best at combat by the numbers. They will end up with the best armor and weapon, as they are the workhorse of any combat scenerio. This was taken into account by those balancing the Fighter, and nobody else. The game's engine is a combat engine, fighters don't need bells and whistles.
There is an implied non-spoken skill system where everyone starts with a 1 in 6 chance of anything. Thieves start with a 2 in 6 chance of hear noise, the reason is because of said implied skill system, which was better designed than AD&D.
The only real problem with B/X is there's no need to houserule it. In fact, houseruling it is almost guaranteed to make it a worse game (See: Labyrinth Lord). It's the only OSR that should 100% be played RAW because whatever bullshit houserules you come up with will break a delicate balance built by people way smarter than you, likely before you were born, and are no longer with us now to explain why you're stupid (Dan Proctor). They even talk about this in the back of the OSE book, any changes they chose to make were stress inducing, because the game is functionally perfect D&D.
They weren't worthy to produce it (to be continued)