Best Module Ever
I have been DMing since 1980, well, I took some time off during the whole 2nd edition thing, however, I love this adventure.
As a player, I had a rogue named Robillard who hired Ogres as henchmen, along with the rest of a standard party, and out of 11 PC's and 8 Ogres, we managed to walk away with myself, the two fighters and a mage, who waited outside during the final battle since he was wounded and the cleric died fighting the fake lich.
As for running it, I love it, not because it is a death trap, but because it is a thinking persons module. By the time your characters get to a level were they can even begin to compete, they are most likely overloaded with gear that you have given them, to much loot is a common problem and modules like this are perfect ways to destroy the one or two items that you should have known that they should not have. It is also a good time to up grade their equipment with treasure rewards for good play and style. I personally add to the module a few rooms of my own, but I greatly increase the treasure at the end.
If I allow them to use their main characters, I offer them the chance to get henchmen and I also give them a strike or two, unknown to them, to help them along, so if they die, it is like a second chance. It is also a good chance for the characters to bond because, now more than before, they have to work together and think of solutions that they have not come up with before.
As a notice of warning to DMs planing on running your characters through this, give them a few items that will come in handy for the final battle, if you notice the sample characters in the back, none of them have anything that could even hurt the thing. Also, don't try and upgrade the Lich to that presented in the Epic level handbook, they will just die that much faster.
The Return To the Tomb of Horror is a hoot. I have yet to run anyone through it, but I have read it, it is just as hard and as note worthy as the first. Basically, the demi-lich is not dead, you have to travel to the home demi plane of the lich to kill him. It is a good story and looks like fun to play/DM, if you can find someone willing to go there after they have cheated death in the first one.
Everyone so far has declined.