Death by camera angle
I really think this game is fantastic in many ways. There are many fights that are truly epic and exciting. What has plagued this series (at least DMC 3 and 4, which are the only ones I've played) are the terrible camera angles. I don't mind losing to a boss because he is powerful, but I do mind when it's the camera angles that get in the way. There are so many examples when you simply can't see where the characters are going because the camera.
I don't think this is going to change. Maybe that's part of the charm of the series. I think it should be fixed because it vexes gamers for no good reason.
Another thing, which I'm sure has been brought up before, is that I feel a bit cheated when the designers are too lazy to design a whole game, and decides to design half and have players play it through twice. Basically, you play are Nero in the first half, and Dante in the second half. Dante has to fight the same bosses Nero does. Somehow Nero doesn't kill them off. Somehow Dante doesn't either because Nero has to fight them a third time! OMG!
Finally, the puzzle game with the dice SUCKS. It's smacks of lazy game design. Sorry, there's no other way to see it.
This game is too repetitive, and it makes an otherwise excellent game into a merely mediocre one. I'm not sure how many newcomers get turned away, but I can imagine it's more than in other games. This is a shame because it means that some players will be deprived of some of the more amazing action sequences.