I'm ongoing fan of the Halo franchise, and have been eagerly looking forward to the latest entry in the series.
Halo 4 is the first entry in the franchise to be done my Microsoft (343 Studios) after the separation of franchise creator and developer Bungie (to be fair, a chunk of those ex-Bungie folks are at 343).
There's a lot riding on the title, both to show that Microsoft and 343 Studios "can do it" solo from Bungie, and to justify the game being the most expensive in Microsoft's history.
I'm several hours into it, and I can tell you -- it's great.
I'm burning through the campaign now, and then will be doing co-op campaign, and a whole lot of multiplayer. More arcade-y than Call of Duty / Modern Warfare franchise, Halo hits a sweet spot for me of pure, unadulterated multiplayer fun. I've got a number of overlapping clans, so I don't waste my time with the stereotypical, racist and/or juvenile effluence of the anonymous Xbox Live online masses. That means I don't have to waste time mashing the mute button, and can use the game as yet another conduit for connecting with friends and game developers around the world.
The campaign is harder -- in a good way. Normal mode on this game is tougher than "Normal" on previous Halo iterations, and they didn't just "dial up the hard" -- there's more complexity to the fighting, and I can't go into every battle exactly the same; which I like quite a bit.
Visually, this is the first new engine in the franchise, and it looks simply stunning. I'm digging the work on the material system and lighting models (though I think "prism reflection" might become the next, overused "lens flare"), and the detail in the characters and environments is (for the most part) top-notch. I had to endure more braggadocio and chest puffery about upcoming lighting changes than I'd like, but I do admit -- looks good.
One of the other things I'm excited about is the explicit in-the-press nod to Certain Affinity -- an Austin indie studio made of great guys who 343 is fully supporting in trumpeting their part in the success of Halo 4 (if you like multiplayer and Forge mode in the new game, you have them largely to thank). There's a good article about all of that GameIndustry.biz.