I gave this game some serious time to age on me. I really didn't want to jump on the 'It's brand new and perfect!" bandwagon. I've spent the past month playing this game daily, from online to offline on each mode type, and I have to say I love it.

Campaign: This part probably gets my lowest opinion out of the whole game.
The length of the game is great, and playing through this with 3 other friends is utterly fantastic, but the things that I feel i was promised so much on just let me down: story points.

The series is not a significant selling point of the series, but considering the genre it's in and the quality of the books that Karen Traviss (also story writer for GoW3), I was really disappointed in the ending. The build up to the end was fantastic, bringing up many old and new questions, and the major plot points built strait up to this...but then it didn't deliver. We get a "fix all" cop out and its just over. I don't want to give anything away, so I'll just leave it as you don't have to kill EVERYONE the second you get a weak shot at them.

Horde: A great change in pace for this already great game type.
The additions of boss fights make the battles feel very intense. The intelligence of the AI is significantly increased from that of GoW2. The best part though, the feeling of satisfaction when you and your friends finally take down that brutal 50th wave on insane.

There are some downsides here though, as with everything else. Though the AI is improved, it still leaves much to be desired; watching run half way through a barbed wire fence and get hurt, just to turn around and attempt to run back through it when he sees you which leads to his death is a little upsetting. This is nothing compared to the inefficiencies of the fortifications that were so highly hyped up. Most of these objects are destroyed by any normal enemy who just walks into them (on higher difficulties is where you notice this most). When playing on insane, building the fortifications, even up to their highest level, is just pointless, as 2 standard locust can walk into any fence a few times and destroy it.

Beast: This is actually one of my favorite parts to this game.
At first, 1 minute to kill every COG infantry sounds insane, but hop online and grab a few friends, and you'll find that's it's more than enough.

Charging through things as a Berserker, healing injured enemies as a Kantus and stunning enemies with the Wretch shout are just a few of the things you can do, and when you combine these things with good teamwork, event the baddest COG units can't stand up to the might of the Locust horde.

Versus: The part I looked forward to the most.
Don't get me wrong, the increased speed, the new guns, the new characters and even new maps are very welcome additions to the series...to an extent. Here are pros and cons to each of these:

Turning up the speed
Pros: Getting into the action never feels as thrilling as charging strait toward your enemy and obliterating him right in front of all of his allies. With the speed way up, you can get around corners and take out unsuspecting enemies faster than ever before...kinda.
Cons: The run speed has been turned up, but the evasion speed really hasn't as much. Where as in GoW2, you can bounce from wall to wall then immediately around a corner to assault your enemy, in GoW3 there feels like there is just a slight delay between hitting that wall, and rounding its corner, often giving the enemy the advantage in a quick shotgun shootout leading to an untimely death.

New Guns
Pros: Assault rifles, which I call new because they all function so differently, now are useful! You don't have to charge in with a shotgun to get a kill, just let them come to you and surffer for it! The oneshot is fantastically fun, the flame grenades do a great job of stopping enemies in their tracks, and the ink grenades work now!
Cons: You know what I'm about to say...the Sawn-Off Shotgun. Before you get upset with the statement, continue to read this. The gun itself is not the issue with multiplayer, it's the playstyle its breeding among the community. It really turns every corner into a camping style choke point, much worse than it was before. You can watch a person run strait to you, and if he misses, you now have to watch a character run and flip every direction waiting for their length reload to complete, then attempt the same thing again, rather than try to actually have an intimate battle, which is what really dragged me and many GoW fans into this series.
The second weapon complaint is the Torque Bow. Maybe it is just something to do with how the server handles shot detection, but the gun now seems to have a slight delay from when the trigger is released, making me miss all too many shots I would have made in GoW2.
The final weapon issue is the grenade. Though they added a bit of a delay from when the sound is played to when it detonates, which is a welcome change from GoW2's instant explosions, the blast radius is about that of an atomic bomb, making escaping the blast radius nearly impossible without the aid of a wall.

New Characters:
Pros: What's there to really hate here? Who doesn't want to customise their online personality in a shooter a little bit, right?
Cons: Well, if the characters all worked the same way, it would be perfect, but unfortunately, contrary to what Epic claims, not all characters actually have the same hit boxes. You can find numerous videos on youtube showing you exactly how different they are, but the main issue here is when you have a female character behind cover at the same elevation as you are, you cant actually hit them with any shot. If you're MOST male characters, a well aimed sniper shot can take off your head. This is a large disadvantage that keeps me playing as females throughout the online experience.

New Maps:
Pros: New maps with new texture designs and plenty of easter eggs equals a great night. When I first jumped online and saw how great Trenches looked after the beta changes and tried it out, it's just really fantastic.
Cons: I believe about 4 of the included maps are not balanced correctly. The developers of GoW seemed to have grown with the concept that Warzone and Execution were their basis for game design online, but then never took into account how very different a Team Death Match setting really is for a game. Rushing a high point for a power weapon is a great past time when you know you've only got one life and you're not going to lose it by camping off by a spawn. Now when you've got a set amount of respawns, it's much less interesting to come charge out of your spawn to be destroyed by the same people who have had the high ground spawns since they got there at the very start of the match. The biggest issue, these high ground points have FULL map view in most cases, so anyone with a decently trained shot and at least a power weapon or hammerburst can drop you before you get anywhere important. And this issue, which I believe may be very close to the worst part, eliminates the joy of 40% of the released maps with the game.

But do keep in mind, this is all just the opinion of one major GoW fan, and I'll play it to the day the next one comes out like you will if you actually read this all the way through.

Over all, this game does deliver on most of its major flashy points so I'll say this gets a good 8.5/10.