Very different level layouts, and the 'test your strength' areas to earn keys instead of exploring great idea.
Some tough fights around.
Good sized dungeon, though I felt it sometimes ditracted having to walk around so much!
Kind of a kicker when you get to the end and realize you have left half the keys higher up in other levels!
Playing the cemetery of the dead etc level - I just really loved it... The end levels were cool too to fight through.
Walking around so much testing walls and forgetting which way I came half way down a corridor.
Too many sprawling corridors more than balanced by some nice level layout/level puzzles, the test your strength part and evil fights.