If you have not played DW yet, it is because you are a piece of shit and I hate you. It doesn't matter that the game isn't officially out until next year, don't give me that excuse. You can find the rules here, you lazy ass.
Dungeon World is an official hack of Apocalypse World, which is a so-so story-gamey game that I've read the book for, but never played. I thought it looked alright, but whatevs, it doesn't matter. What matters is that Dungeon World is the best Dungeon & Dragons game ever produced. Despite a solidly modern, contemporary design aesthetic, game play in Dungeon World actually felt more like D&D to me than any edition of D&D I've played. Hell, the game even unironically accepts its roots and uses the language of D&D, with many names taken directly from D&D, such as the Fighter character class ability Bend Bars, Lift Gates, a cute nod to come on you've played AD&D I don't need to explain it.
Maybe it was a fluke, I don't know, but it was really great, and I'm so impressed that I plan on hacking the hack and shoving some Labyrinth Lord into the game to fix the parts I wasn't entirely pleased with, and forming the ultimate contemporary retro-clone. But before I start making a bunch of posts for a system no one cares about, I have to make people care about it.
VERY NEARLY FLAILSNAIL COMPATIBLE
Characters in DW have the standard 6 D&D stats, which range from 3-18. They have the familiar races and classes, like dwarven fighters and human thieves. They gain XP. They have hit points, and smash goblins with hammers and look for gold. You could theoretically port any AD&D/retro-clone character into DW. I believe that DW characters would have the edge on HP and damage, and the armor system is a damage reduction instead of a decreased chance to be hit, and a game master familiar with DW could handle any hiccups and convert spells/spell-like abilities on the fly thanks to the simplicity of the DW mechanics.
...WHILE DIFFERENT IN ALL THE RIGHT WAYS
This isn't to say that everything is the same between AD&D and DW. As previously mentioned, armor provides damage reduction instead of making it less likely a character is hit. Damage is also different, in that the damage dice is not determined by the weapon, but by the character class. Clerics, for example, always deal d6 damage, baring weapons, spells or effects that provide a damage bonus. The weapons themselves are somewhere between Old School Hack and D&D. There are distinct weapons like halberds, or at least weapon groups, such as flails, hand axes and long swords, all three of which are mechanically identical. However, weapons are largely arbitrated, so the only mechanical difference is range and weight, and maybe a keyword or two, which can be purely flavor (the +messy keyword simply means the weapon deals gruesome and messy wounds) or have mechanical benefits (+accurate allows players to use DEX instead of STR when making melee attacks.) Another major difference is the quasi-Vancian spell system. Casters can continue to cast the spell so long as they score 10+ on their roll+INT mod (wizards) or roll+WIS mod (clerics) rolls, with one of the partial success options being that the spell is gone until the caster rests. It's a nice change of pace for the out-dated and, frankly, archaic Vancian spell system.
As for character creation, things are hella simplified. Your class is the major defining bit of your character. It determines your HP, damage dice, and a number of special attributes or moves your character has access to. The race, interestingly, only adds one new trait. As the system has a rough asymmetrical class parity, it means that players can chose to be any race/class combo without worrying about being able to contribute to the parties success (D&D 4e was terrible at this.) One of the other major differences is called Bonds, which I think is an interesting new rule. At character creation, players chose Bonds to have with other characters. These are one-way relationships, although two characters can have Bonds with each other if they wish. These relationships are simple; some examples from the Fighter class include " _______ owes me their life, whether they admit it or not." and "I have sworn to protect _______" Obviously this has narrative impact, but it is also mechanically reflected. For example, attempting to aid a comrade gives you a bonus for having a higher rating in your bond with them.
THE RULES ARE HELLA SOLID, WICKED EASY
Instead of being d20 based, DW is 2d6 based. Instead of the binary pass/fail mechanics that have plagued D&D since its inception, DW has a three tiered success system, where 1-6 is a failure, and 7+ is a pass. However, only 10+ is a true success, while 7-9 is a partial success, which, depending on the move performed, either have a decreased effect or a minor penalty. Let's just see an example, okay? This is one of the "basic moves" which are maneuvers all characters have access to, and covers basic combat like attacking, dodging, making saving throws, etc.
- HACK AND SLASH (STR) When you attack an enemy in melee, roll+STR (Note: "Roll" always means 2d6, +STR means add your STR modifier.) On a 10+ you deal your damage to the enemy and avoid their attack. At your option, you may chose to do +1d6 damage but expose yourself to the enemy's attack (Note: Players can often given the opportunity to chose additional risk/reward scenarios.) On a 7-9, you deal your damage to the enemy and the enemy makes an attack against you.
These "moves" are the basic unit of player action. They aren't just combat moves, it is used for things like diplomacy, remembering monster lore, saving throws, spells, etc. It should be noted that players do NOT simply name their move. It is not enough to simply state that your character is going to Aid the Fighter, you have to explain that your Thief is waving his arms and shouting to distract the troll so the Fighter can stab it in the guts. In addition to codifying common actions in a simply, easy to understand manner, these moves means that the rules for things you can do are always at your fingertips, right there on your character sheet. This isn't to say you are limited to doing just the moves you have! The system is simple enough that GMs can easily arbitrate any action by picking the appropriate stat, adding a bonus/penalty, and then narrating the failure/partial success/success.
SOME NARRATIVIST HOGWASH
My biggest complaint about the system is that there is no initiative queue at any point in the game. Whomever wants to go next just does. Mechanically this works out: one player can not simply take turn after turn because the game master can take turns when they want as well. In fact, this can lead to interesting situations where, say, the other players step back to let one player have a one on one duel in the middle of a raging battle. That's neat, I like that.
The problem is that, well, some players are idiots. Every group invariably has that one, uh, decisive player. Since they are quick to act, they are going to be acting more than other players. This is a problem with the Apocalypse World system that DW is based on. It isn't exactly difficult to add an initiative system, but there you have it.
The other thing I don't care about, although it's less that I dislike it, and more than I'm neutral, is the DM tools. I'll be honest, I find them constraining. I tried sitting down and using Fronts and whatnot, and it gave me flashbacks to high school where I had to turn make word webs or outlines before I was allowed to start the essay. Hey, maybe it's your style, I don't know.