So was thinking about the monsters in DW. My answer to the question is yes, and no.
1. No: Location
The initial monster content (monsters of dungeons) wasn't all that useful for me. Why? Lets set aside for a second 'classic' D&D dungeon design (which makes somewhere around zero sense to me personally).
In most campaigns there are specific themes. If the mad wizard Zorgon makes clockwork beasties for his dungeon, you're unlikely to put in Ankheg's and Ropers. You probably want some golems and elementals as a starting point for example stats, or included monsters. Hence that section of the book is probably completely useless at this point, because unlike true D&D re-skinning stat-blocks and 'balance' aren't applicable so re-usability is kind of minimal.
Moreover setting specific monsters (ex again: ankhegs and ropers) are far less likely to be useful in an off-the cuff game, rather than a D&D clone.
I personally am a bit put off by the crazy unexplained ecology of locations (so ... in a few connected rooms that cover about a city block, you have two kobold tribes, some undead, five different kinds of apex predators that can challenge well trained and well equipped humans, some traps and everything carries coin. ಠ_ಠ). So I'm unlikely to just pick up the book and throw down whatever I flip to into the dungeon. So in this sense, this is unhelpful.
However, what you're adding is very valuable in different ways.
2. Yes: Theme
Your monsters aren't conceptually very different from what we see in generic fantasy game X. Yet the 5-6 line description of most of the monsters you write will spring entire adventures into my mind. They are the same monsters I've seen a thousand times, but filtered in a way that works with my brain (story vs statblock).
I'll provide an example: Sahuagin. Seriously how many people have campaigns full of these guys? Water and swimming rules are a pain, and they're low level enough that you usually substitute the staples (orcs, goblins etc). Then I read your description and I get chills. There's this crazy, creepy, Dagon and Cthulhu meets Insmouth feel to it. I realize these things are f-ing scary. And if a boat leaves the sight of land, they better have a weather-witch on board to sing down the Sahuagin, or they'll all wake up with cold fishy fingers clutching throats as mouths filled with teeth work on their bellies.
So I read this tiny six line blurb, and boom. Adventures, flavor, theme. Sweet.
3. Yes: Example
So your rules on monsters are clear just fine, but examples really help drive the point home. I'll try to demonstrate.
I read the stats on an orc berserker. 20hp, 0armor, cool. Then dragons show up. Iconic, badass, sweet right? And my first impulse when glancing at them is to go SIXTEEN HITPOINTS? Are you kidding? That's like 3 solid rolls. You can't be ser... and then I look again.
I read their tags. I think about how the fight feels in my mind. Messy. They don't just hit you for fifteen damage. They rip off your arm. Their breath attacks whole sectons of the battlefield. Terrifying. You have to stop peeing you pants just to run in praying you don't get incinerated before you even engage. Weapons frequently bounce off their hide.
Man. Doing 16 damage in that scenario is next to impossible. Not just that, but you're probably going to be crippled, even if you win. The STORY behind the moves they have really hits home. And this example teaches me both the difference between Orcs and Dragons (who stat-wise aren't super dissimilar), and how to set up similar opponents.
So even though the rules for making said monsters are laid out clearly, it isn't until i *see* this that it really sinks in and brings it home.
(edit: fixed HP, didn't recall difference between Dragon and Apocalypse Dragon)
4. Yes: Campaign
So, last night I ran a game (it went great, writeup is coming). Our fighter is a scarred elf. She decides she got the scars from being captured by orcs and being made to fight in an arena. We build on that, and soon we realize the orcs are waiting for the spring thaw to end so they can cross a major river and they're only days from the nations capital.
I flip right on over to your 'hordes' and boom. The orc encounters are varied within the same 'type'. They're flavorful. They have tactical bite. I add a dash of some other evil things that get summoned by shamans and lead the war-horde. But the core holds really well.
What I'm saying is that while I appreciated the dragon, this specific section is the most benefitial to me, and to the style of game I prefer to run. (Ex: Undead, gives me good variety, and nice flexibility within the same theme) To be specific - by doing iterations on a theme you provide immediate framework for me to generate a unified threat/danger without having to do additional work myself. Sure the Sahuagin in my little Insmouth idea above probably have a champion, and maybe a giant squid to back them up, but I have to write it up.
So the hordes, and unified fronts (like undead) rock for me.
Hope that helps!
What about everyone else?