I played another game of Labyrinth Lord the other day, in what has been a very successful campaign (details here). This game was... less successful. Three characters dead and a group of very frustrated players. It was a downer. We all left feeling a bit down on the whole experience, feeling like there was a lot of risk for very little reward. I'm following the dungeon stocking guidelines pretty scrupulously, so I'm a bit frustrated with the game.
I think I'm going to have to rethink the way I design my dungeons, but the whole "planning for the party's level" is one of the things I got sick of in 3.5. I want to just stock a dungeon with what I think is cool and interesting, and have the players interact with that. On the other hand, I don't want to promote the kind of "take three hours to traverse a 30 foor corridor" paranoia either.