That should be ovious, no game with over a hundred different dungeons is going to be able to have every single one use a completely unique tileset. But even so, there's certainly room to make dungeons which use the same tileset feel distinct from each other, through creative use of the resources available. It helps a lot too if you put interesting things in dungeons, and mix up tilesets on occassion. Having a cave lead into a forgotten ruin does a lot to make the cave feel more memorable than just a plain cave. With Skyrim's larger number of dungeon designers, I expect the dungeons to be more varied than what Oblivion offered. Obviously, they won't all be completely and utterly unique, but I do hope to be moe satisfied with the ones in Skyrim than it's precessor.
I know. I was ever expecting all 120+ dungeons to be 100% unique. I'm just hoping that they do mix up the layouts sufficiently, and I hope that I'm not going into a dungeon that looks similar to 25 other ones I've been in, just with different loot.
My main point is I guess, I just hope that by "Handcrafting" the dungeons, they don't just mean customizing the loot, or enemies by hand, but actually customizing the layout of each dungeon within the 5 or 6 "archetypes".