So far, not vastly difficult. It's not as hard as Devil May Cry (anotehr comparison, because they are so similar) but challenging. The game is more generous with allowing saves before big fights is the big difference, so while some bosses might be a challenge, the game allows you to load the game right before them and not fight 3 in a row before the next save point.

Call it a "fitting" diffuculty. Opening video is rather good too.