So, in the snapshot a few weeks ago there was an option added to customise world types however you like. With the addition of water dungeons in today's snapshot, I decided to try some out. The water dungeons are awesome, although kinda creepy. Can't wait to get them on VC
With the custom worlds, you can change pretty much any aspect of the world. One feature I was interested in was the "Dungeon Spawn Change" slider. By default, you can make it up to 100, which spawn a dungeon once every 6 chunks or so. I decided to test some stuff out. With a little nbt tweaking, I managed to make this spawn chance go from 100, to 100000. This was the result.
When I created the world, it took about 5 mins for anything to actually generate. Even then, the chunks I could see were limited. The constant spawning of dungeons killed the game. Console was spammed with "Running behind. Skipped 18450 tick(s)" and FPS was like, ~10.
TL;DR: Don't overload your game, no matter how cool it might look