The campaign will take you less than 10 hours to complete on Normal difficulty, but there is some incentive to replay the story because you can unlock hidden endings by completing the higher challenges. You can also add Skulls to the game, which are options you can select when starting a level that will adjust some of the basic rules and settings for either you or the enemies, like disabling your motion tracker or forcing you to completely restart the level when you die. The extra level of variety is welcome on repeat playthroughs or if you want to add a new challenge to co-op.
The multiplayer has an interesting twist in that the whole system is presented within the context of the Halo universe. When you create your character in multiplayer, you're supposedly a Spartan IV that's assigned to the UNSC Infinity, and any armor, skills or weapons you've unlocked can be used in any mode. Gameplay is split between the cooperative Spartan Ops and the competitive War Games. Spartan Ops, rather than just being a checklist of various challenge missions, actually has its own storyline, complete with cutscenes, which runs around the main single player narrative. 343's current plan is to release free 5-mission Spartan Ops chapters over a designated season.
For a lot of players, the real core of Halo 4 will be War Games, which take place on Halo's equivalent of the holodeck housed in Infinity's massive interior and are run for the Spartans to hone their skills fighting against each other. On the whole, the War Games mode delivers a healthy mixture of old and new. Mainstays like the Slayer game type and the Blood Gulch map - resurrected as a new map - will keep old fans smiling. If you ever get bored of playing the game maps, you can always jump into Forge and create something custom, or just play around making Rube Goldberg-esque sequences. It can be fun to blow off some steam by adjusting the gravity, spawning with rocket launchers or just adding a ridiculous number of tanks to a level.
New to the series are ordinance drops. Weapons will spawn on the map like they normally do, but players will also be able to call in personal drops upon filling their ordinance meter. The meter fills by killing players and performing other specific conditions, like ending a player's killstreak. Personal ordinance drops help to alleviate the mad dash to or camping around weapon spawn points, but it can sometimes lead to a dominating player becoming more dominating. Halo 4 maintains the weighty feel to its multiplayer combat. The Spartans are sturdy folk in their armor and shield - not easily brought down - making firefights less about who shoots first and more about landing several shots accurately. This pushes the gameplay towards learning the weapons so you know exactly how many shots are needed or comboing with grenades and melee to quickly take someone down.
Bottom Line: It's going to feel a little off with a new studio taking over the franchise, and Bungie left a big mark on gaming with Halo. While 343i shouldn't just try to make a Bungie game, the single player isn't up to the series' standard. Halo 4 does balance that with a robust amount of content across the various gameplay modes.
Recommendation: The continuation of Master Chief's story feels a little thin, but War Games, Spartan Ops and all the other multiplayer offerings Halo 4 will keep you playing for months to come.