Personally, I just roll a random encounter each time anyone in the group takes a 20. This has the added effect of adding traps that are triggered by taking a 20 to disarm a trap. I think it makes it a little more interesting.
As far as search checks go, I tell my players how many people they can get to search an area. This has caused them to creat "Search Teams" in order to more effectively aid each other in a search check.
I decide on a timing mechanic for automatically shutting doors. The mirror room in B I had shut behind the first group of guys that went in. I basically asked everyone who was going in and who was staying out. All who went in were trapped inside, and those that said they stayed out were trapped outside. Other rooms had longer delays, or specific triggering mechanisms either in place already (such as the alcove with the defending quarterstaff in B) or I just made one up that seemed appropriate.
To Jim, regarding what you would change:
Encounter conditions are good, but things like noises and minor tremors, especially in rooms where there is nothing else, makes it hard to convey those things to players. I use them to the best of my ability, but since I run in a game store where there are distractions, it makes it tough to set a mood sometimes. I also find some of the room descriptions to be unwieldy. This is mainly due to the fact that there were room descriptions written as if the PCs were at one of the doors, when it was very possible for them to come into the room from a different door.
I agree that the dungeon should have been long instead of square. That would have made it easier for me and the group to go from start to finish. Especially if you start ramping encounters into the epic range at the end. Like the Kraken in L being a psionicist or something crazy like that. I think it would have given it a more Ghouls and Ghosts or Castlevania feel (one of my favorite all-time video games.) Especially if you have sections of the dungeon go up or down in elevation changes. That could have accounted for the inclusion of submerged regions as well as high elevation regions.
Having something on the order of 8 regions of the dungeon (I'm lettering alphabetically, not necessarily by the regions that would be included) where A, B, and C are on the same level, then the PCs go further underground (either a hole created in the floor of the dungeon, or a gradual sloping further underground) where D could be shallows and swamps and E could be the deeps. Then an ascent back up to F and G (which could be the climax, creating a hole in the roof of the dungeon) and then a climb up steep mountains with Giants and flying creatures and such to actually escape the dungeon. This would even allow you to have different climate conditions in some of the regions. A, B, and C could be standard fare dungeon (with C similar to I, just to keep with all of the different bizarre themes with some of the regions in the dungeon) while D is swamps and shallows, E is deeps, F could bring the PCs up through a volcano for a fire-oriented region, followed by a surreal kind of region that would be either the equivalent of N, D, or G (depending on your preference for a climactic region) for region G, and then H could cover your cold weather and aerial encounters.
Damn, makes me wish I could go back and start again (almost.)
Thanks,
Howard Hooven