Devil May Cry 4 is a very, very good game and is great fun to play, as well as looking absolutely amazing. The new character Nero adds a lot to the series and is different enough from Dante to make you feel they actually put some work into the character development.
The gameplay is very slick apart from a few dodgy camera angles in places, attacking feels fluid and satisfying (especially with Nero's arm, which is simply put the best weapon in this type of game ever for the variety it adds to combination options) the bosses are in most cases huge and interesting, and the ability to switch styles at will with Dante adds a new dimension to his play as well.
The game is not perfect - especially in the second half where Nero's levels and Bosses are essentially repeated (in reverse) as Dante which although ties in with the storyline does seem a little lazy. The games difficulty seems to have been lowered considerably from Devil May Cry 3 meaning gamers with experience of the series will fly straight through the game without much of a challenge, but with harder modes to be unlocked upon completion this is not really an problem.
Another thing is characters, as far as I can see you get Nero for part 1, Dante for part 2, Nero again for the final as per the storyline - although Lady and Trish do appear in the cut scenes completing the game does not unlock them? Not a massive issue but difference adds to longevity.
Overall, as a fan of this series and action games in general I am very happy with this game and judge it as money well spent. The couple of issues I had are not really that important but do stop this getting a full 5 stars, don't let that bother you too much though, if you are an action game fan this one does the job.