RATING: Go buy it, just don't expect an awesome story and enjoy it for what it is.
I've been meaning to write a review for DMC4 for the Xbox 360 for a while now. For the time that I played it (before lending it off to my brother), I did enjoy the game, and played it for quite a while. I played starting directly in DEVIL HUNTER mode (I skipped Human mode entirely) then I finished the SON OF SPARDA mode a few days afterwards. Finishing SOS mode took about a week because I would intersperse playing SOS with the 'Bloody Palace' mode that gets unlocked after beating the game once.
The thing that stood out for me the most about Devil May Cry 4 is the gameplay. At Devil Hunter mode, learning how to mix up attacks and combos is pretty important, especially in later levels when faced with tougher enemies like Angelos (who can block your attacks quite easily). The game has a system which lets you buy new abilities by earning Proud Souls. You get these after each level. You can also improve your character by getting Red Orbs which let you increase your health and spirit energy.
I also found the boss monsters quite challenging in my first playthrough. Later on, since the game makes you fight the boss characters over and over again, you'll figure out that there are certain techniques which make fighting them easier.
The cutscenes in the game are very well-rendered; they're testament to the power of Capcom's MT framework game engine, which I think is superior to Epic's Unreal Engine 3. Unfortunately, in terms of story content, the cutscenes don't really have that much . The story in the game is really, really simple, and I'd say that it's just there to put a bit of purpose to the action (if you must know, the story is a lot like Mario....'save the princess' then save the world in the process). I don't really have a problem with the simplicity of video-game plots; so long as the game is fun and the story doesn't get in the way of delivering an overall great 'game' experience, I think that a game is worth recommending. I could spend a lot of time nitpicking story points but I realized that this game wasn't really meant for that purpose. The action in the game is top-notch and very challenging (if played starting out with DEVIL HUNTER mode). I skipped HUMAN mode because I heard that this was the mode in the demo of the game (downloadable from xbox live). I found the demo to be less than appealing in terms of challenge, so for the full game I decided to go straight to Devil Hunter mode, and thus I had a more enjoyable experience.
Another thing I really enjoyed about DMC4 was the Bloody Palace mode. This is essentially a survival mode, where you have to stay alive and beat all the enemies before the time expires. From what I've read this is about 100 stages, and thus far I've only been able to make it to Stage 20+ (after fighting the boss, Berial). It's a great way to explore the gameplay options available to each character; it lets you learn more about the available combos and skills and how to use them effectively.
Perhaps the only thing that I didn't like about the game was the fact that it makes you fight some of the boss enemies over and over again. I wish that Capcom introduced more scenarios instead of teleporting you to the boss area instantly for some stages. I did enjoy one boss character in particular, and that's Credo. He offers the most challenging fight in the game (when you start out, you don't have that many abilities; perhaps that added to the challenge factor). He's also a well designed character and one of the more interesting new additions to the series. It's just too bad that *SPOILERS* they kill him off pretty quickly *END SPOILERS*
Also, it's a bit unfortunate that Dante seems to overshadow Nero at every opportunity. Because they had Dante in the game, it seemed to me that Nero appeared more like a secondary character for the series. From what I've read, they were supposed to pass on the torch to Nero as the new hero of DMC; but based on this game, Nero just doesn't seem as interesting as a character compared to Dante. Nero also doesn't really get that many moments to make his character more interesting for players. However, maybe that's only because it's obvious that developing a good story wasn't really the emphasis for the game design of DMC4 to begin with. Nero does get the Devil Grabber/Snatch ability (thanks to his arm), which makes him superior to Dante in terms of executing continuous combos. That said, I hope that they just pair these two characters up again for DMC5. I don't think Capcom should retire Dante yet.
Overall, DMC4 gets my recommendation, for players who want a game that has challenging gameplay values and if you're willing to overlook the lack of story content. This game made me interested in the series (it's my first DMC game, by the way), and now I'm looking forward to DMC5, which will hopefully be made for the current generation of consoles.