I used all of these dungeons as "I need a dungeon in a hurry because the players went off on a side quest" and they worked pretty well. Even the Citadel of Evil, which I initially thought seemed small, turned out to be very worthwhile. All of them got serious use - at least two sessions apiece from each of them with Praise the Fallen needing one big initial session that was a prisoner break-out then a later three-session return to clear it out completely.
Running through them in order encountered by the players:
Praise the Fallen has 15 A5 pages with lots of interesting bits and pieces within. They got to do a bunch of creeping around some of the nice old school spooky things like statues of angels and so on. Some proper old-school traps like compulsions to fling yourself on a blade were good and unsettling even where saves were made.
On the initial excursion the party missed most of the really nasty stuff - they probed the front bit, got into a big fight with a gathering of cultists and prevailed by bottling them up in a room and liberally using flaming oil. Solid tactics and good use of terrain. They did a bit of further creeping around, decided the spookier, deeper rooms were way over their heads and withdrew with the prisoners they had rescued.
The dungeon lurked in the background, oft mentioned, for much of the rest of the campaign until the party finally decided to go in and neutralise the threat. This return was supposed to be a quick raid (according to players plans) plunging deep into the temple to root out the cult leadership. The first session of this 'final' raid went well for the party as they ambushed cultists, sneaked about and bluffed their way past scattered lowly cultists with stolen robes and their acquired lore. The second session, as they ventured deeper they managed to pass many of the set piece wards and guardians using 'pass-pendants' before rousing a very large cave monster and having to fight them on treacherous terrain which left them low on resources and hit points to end the session. They staggered from that into a next set of guardians for the third session, fighting their way through and then getting into another big fight to stop a summoning. This brought out the dungeons arch villain who was invisibly nibbling them to death with summoned minions before they finally managed to reveal them and land the killing blow, just above the initiative tick where the villain was about to flee and become a recurring pest.
The dungeon itself is really nicely done. You get an intro on one page, some notes on rules applicable for the whole dungeon then a random encounter table and the main villainess. A small, total map is then followed by section-zooms with room-by-room detail. There are nice touches like the numbers of the rooms on the margins - a one two three up in the top corner so as you are leafing through you can quickly see where your where your room is. Stat blocks appear on the page where where you should be using them, descriptions are pretty terse, BX-style. The map is doing a lot of work with proper detailing of stairs up, stairs down secret doors and the likes. Good information density overall. I ran it pretty much straight out of the book.
My only advice is to be enthusiastic about rolling encounter chances - you will not always get them and even when you do, not all of them are going to be serious challenges, so roll often to keep the pressure up.
The Citadel of Evil was an identified location that the party knew they were going to go to so went relatively prepared and this ran over three sessions - one getting to the site and scouting from outside, one session of full-on dungeon-bashing and the last spent scouring the now-pacified wreckage for lurking remnants and/or loot.
They worked their way in through the base, up through the mysterious rooms in the middle, focussed on rescuing prisoners of the inhabitants so less on prying up flagstones and loot to start. The whole thing was a nice combination of slightly mysterious design requiring some careful scouting, non-traps that still needed navigating and then lurking cultists for active danger.
My party spent a session working their way up to the core then got in a fight with the main villain and managed to set a serious fire in the staircase that leads up to the citadel above. They did accelerate that fire but effectively they got into the basements and set the whole thing on fire above while they rescued people and fled. This bypassed some fighting in the upper structure but those foes were mostly guards/not the most interesting thing going on.
Then they did another entire session of poking through the ruins, interacting with traps and dangers and the hazards involved with the burnt out husk and the things rising from the dead and so on.
The dungeon is written to cover two pages so this was incredible bang for buck. Very good stuff, got two solid sessions, ten hours of play out of one side of A4.
The last one was the one on the dust cover, Zaratazarat's Manse, where a wizard was wizarding and cooked up a hazardous artefact that has gotten out of control. On this occassion the artefact is he's made "Ragga Gyxy’s Random Encounter Table", basically a monster summoning slab. This was a place the party was pointed at when they asked a settlement 'what kind of problems have you got' and then decided to poke into it.
I did not use the external village as written because I dropped it into an existing campaign but apart from that, I used everything over two sessions. One was an initial reconnaisance by a semi-open table group and the other was by the rest of the party to clear it out.
In both cases I used the mechanics provided - the big random-encounter table, the per-room encounter ladders, the 'find-the-wizard' rolls, the reaction rolls - which were fun. All of this on the inside of the dust-cover for the magazine so quite small text but still functional.
The first session, the party got there, poked around, ran into some random-encounter generated monsters and met some with negotiation, some with swords drawn. They managed to stumble their way past a bunch of things directly to the wizards bedroom and got in a big fight with the mimic-door there, then spent a block of time dealing with the sketchy magic mirror before leaving with some rescuees.
The second time around a slightly different team went in and went room by room trying to figure out what the problem was. They eventually made their way downstairs, took out the artifact that was malfunctioning to spawn all the monsters and installed the wizards apprentice as the new master of the place before leaving with armfuls of loot.
This is the most complex of the dungeons because there are lots of moving parts - more punchy random monsters, large uncertainty over if/where the wizard is found - and the fact that many of the monsters are sentient and randomly summoned from all sorts of places means they may not be hostile or from this world. I had fun having a dwarf be a warhammer old world dwarf, a white ape be a Barsoomian, etc.
From the inside and outside of a dust cover, let's say two and a half pages of A4, I got two solid sessions, great gaming.
I got great use out of those dungeons - while one could make arguments about room for improvements in any of them which other reviews have done, I think the combination of having a bunch of them in a compact format was very useful indeed when running that open format hexcrawl. The players could roam where they willed and I had kick-ass dungeons at my finger-tips whenever I needed them.
In full transparency I must admit this was not the *most* weight efficient way possible to carry those around since Knock #1 is a chunky book but given the minimal effort involved in pulling it off the shelf and slinging it in my go-bag, I could commit the calories to lug it around.
