I ran this module twice, never actually played it.
The first time was back in the early 1980s. I dutifully stuffed the dungeon with monsters almost at random. There were tribes of orcs living next to ogres, fire beetles stalking the same halls as kobolds. I like to think of it as a time when the monsters of the world got along in peace and harmony, united by their desire to eat adventurers.
The players hacked their way through it, with the chamber of pools and the wizard's lab providing all sorts of fun. I think the party's NPCs served as taste test subjects for the pools and test tubes - at least one NPC was forced to eat ancient, dried dung.
(Hey, we were 10. It was funny at the time. This was also back when the party's idea of checking for traps was to throw the NPC thief into a room, close the door, and listen intently for explosions or screams.)
The big innovation this module gave us was in the stat boosting pools (or some other contraption) on the second level. I had recently bought Deities and Demigods, and in an effort to test out the rules for stats over 18 I allowed the players to boost their stats to ungodly levels. We ended up with a few 21s.
After that, I remember buying The Fogotten Temple of Tharizdun, which also had a stat boosting doohickey. The players were pretty eager to sack the temple, swear undying allegiance to Tharizdun, and get that +1 bonus to Strength, Con, or whatever, but we ended up ditching the campaign when we figured out that we were being total munchkins. Our next campaigns were much more normal.
The second time was shortly after 3e came out. I stocked it with monsters again, though this time I had a plot and reasonably coherent encounters. The basic premise was that the PCs find a treasure map that leads to Quasqueton. Unfortunately, so do about 5 other groups of monsters, explorers, and treasure hunters. After battling the orcs who had set up camp in the halls, the PCs had to deal with a massive influx of country bumpkins eager to make a quick buck by looting the place. There was a dwarf demolition team blowing holes in random walls (and unleashing all sorts of nasties - I decided the Zelligar had a thing for summoning demons and trapping them in pentagrams for later use; of course, the dwarves kept accidentally blowing the pentagrams apart) and the halfling con artists who set up all sorts of fake, cheap treasures and sold maps leading to them. It was a blast.