Given this, it took me a while to hone in on the essence of what I like about Dungeon World in particular. It is because it uses a discussion model to moderate/manage the interaction of the players, GM and mechanics, rather than a wargame or board game model which has become the default for most RPGs. Whether we are aware of it or not, most RPGs use their mechanics much like that in a wargame or board game given the roots of the hobby. This is especially true in areas of conflict and high tension, where mechanics are used to avoid the whole thing resorting to a "bang, you're dead" exercise. In many RPGs, this shift is light, almost imperceptible. In others, its quite obvious, such as in D&D 4e. Either way, we end up with the concept of "turns", "turn order", "actions" etc, which has little bearing on the actually flow of what's happening other than to break things down into manageable chunks and provide a level of certainty.
Dungeon World doesn't do that. Instead, it uses the concept of a discussion to moderate/manage these moments. Someone says something, and the other person responds, back and forth. What a discussion is is not something that we may think about too often, but everyone understands the concept well and I think we would all realise when something said feels forced or breaks the usual flow in a discussion. As such, it provides a less intrusive way of dealing with those moments of conflict and high tension with some level of certainty. The RPG ties this into rules use simply by have specific narrative triggers for each rule and also explicit rules around the flow of discussion.
Now, I know what you are going to say. "Sure, but that's how I have always done it". And that's right. A lot of RPGing uses this model already. In general, it is during combat that the wargame or board game model takes the fore. Even then, some GMs run their games almost in their entirety in this way. I use the discussion model for combat in Cons and it also works for some RPGs like Call of Cthulhu, where initiative is kind of irrelevant. It is also worth noting that this model is not necessarily better than the wargame or board game model in that it decreases equity of action and some certainty (which in some groups would be untenable). In exchange though, it provides less intrusive way of dealing with moments conflict and high tension, empowers the GM more to make the action exciting and increases overall flexibility.
In any case, the reason why this definite shift appeals to me for Dungeon World is twofold. First, I think it opens us D&D to new players. D&D is often seen as the uncool kid on the block. This is partially because it is the poster child for the wargame or board game model, which it introduced to the hobby. It has also become increasing mechanical, shifting toward an specific set of terms and rules. For many RPGers, it no longer provides the best entry in the hobby as they aren't interested in that model and find that flow of play to be unnatural. Second, I think it also captures one of the main appeals of old school D&D, where much of the gameplay was created not from the application of rules but from a discussion between the GM and player. Interestingly, Dungeon World does this whilst circumventing much of the debate around rules v ruling. It has explicit rules, but they don't exclude rulings.
Don't get me wrong, Dungeon Would is not the be all and end all of D&D RPGs. I remain a fan of D&D first and foremost. I think that 4e's exacting use of the wargame and board game model is sublime, the madness of the AD&D1e ruleset is fun, Moldvay's B/X is the soundtrack to my youth and Castles and Crusades' ability to capture the essence of D&D regardless of edition to be awesome. Dungeon World just provides another avenue into that world of awesome that I can travel down with old and new friends. And that is why I like Dungeon World.