Oh wow, I beat a DMC game and didn't break anything in the process.
Story: Some have said that DMC's story is not its strong point, and when put up against its gameplay, I suppose that holds true, but regardless, DMC4 tells an interesting story from the outset, but there's no denying there's a strange emptyness in the first half without Dante. Nero turns out to be quite a capable hero and really avoids driving the series into the ground, like many thought he would. The ending actually gets pretty emotional, but Dante remains as humorus as ever. Of special note, I think, is the scene in which he gets Lucifer and his epilogue. In short, even if you don't play DMC for the story, which is understandable, it'll keep you entertained enough to keep playing.
Gameplay: Well, what's to say? The action is as tight and fluid as ever. Nero's Devil Bringer is an invaluable tool and adds a whole new dimension to the combat. Learning to use Exceed will really save your ass as well. Dante acquires several unique and fun weapons, but nothing that I believe truly stands out.
Sound: The game's soundtrack holds up well enough, but the battle song and ending theme, "Shall Never Surrender", which is surprising enough to find out is the same song, really stands out. Aside from the music, most of the voice acting is good, but some of the characters are probably better off silent, like Credo.
Overall, I think DMC4 was a step in the right direction for the series. They implemented a new main character without him hijacking the series, and that takes some skill. IMO, they should keep Nero around. Obviously, it would be insane to keep Dante out of the next title, but I think the two heroes can share the same spotlight equally. It'd be cool if Nero joined Dante at Devil May Cry...hey, just saying!