Yeah the whole "lets not include a note saying "installation disc" was a bit dumb by 343 I'd have expected more. I've played some Halo 4 now and control wise it's pretty similar to CoD; left analogue stick pressed in = sprint, crouch is now the b button (hell I keep holding it wanting to go prone!), melee is on the RB button and grenades on the left trigger. Pretty much once I got the idea to play like it was CoD my skill level went up a fair bit on the multiplayer games we did which was disappointing because I prefer playing halo to mean playing halo.

I noticed a few things removed from the game:

Hornets and/or Falcons (seriously the UNSC seems to have forgone any form of air power in 4 why I don't know)
Dual wielding (not such a major loss but there were times and weapons where dual wield became useful like when needlers and plasma assaults were dual wield weapons)

Some of the changes I'm unsure about, things like the new Warthog look or the sound of it's engines they've gone for an added touch of realism the hog now sports jerry cans bouncing over the rear, firing it's cannon is now accompanied with a tinkling sound of shells hitting the deck of the hog, they've also made it so it can overheat it's cannon meaning you're unable to simply drive constantly throwing down bullets (done the same with static turrets too) though the hog and the mongoose appear to have had some pretty beefy armour moulded in to them as a direct hit from a rocket launcher won't always kill a mongoose but it will kill the rider of the vehicle.

Whilst yes, the Hog now sounds meatier, and more raw it's a fundamental break from the Hog we know and love from Halo (if we go chronologically of storyline - Wars, Reach, CE, 2 & ODST, 3) which I'm not so sure I agree with since if you look at when these games are set: Wars is 20 years prior to CE (don't get me started on the idea of introducing flood in this game), Reach is just before CE, 2 is I believe a year or two after CE, ODST is during 2 and 3 directly after 2 with Halo 4 set 4 years 10 months 7 days and 16 hours (or whatever it was Cortana said) after the events of 3 (to give it a better sense of scale, the difference in terms of time passed between Reach and 3 is under 4 years as Cortana is the AI transported to the Pillar of Autumn by Noble Team on Reach in 4 she states she was created 8 years ago) the idea of nerfing the warthogs trademark constant stream of bullets or placing jerry cans on it seems to be wrong in some sense.

Another change is that the Ghost when damaged no longer sparks blue plasma energy everywhere it smokes as if it was a UNSC vehicle. I've also noticed that the Halo Reach Banshee is the Banshee that makes a return to service in 4, this doesn't fit with the idea that the Banshee in 3 was different due to upgrades in Covenant war tech, the Storm Rifle is another issue, the gun works and looks more like the plasma repeater from Halo Reach too. Plasma Repeaters were pre-cursors to the Plasma Assault Rifle and Heavy Plasma Assault Rifles of 1 - 3. I'm not sure where 343 thought they were going here I feel like the stuff they/Bungie announced to explain the changes between technology between 3 and Reach are being ignored in favour of not having to re-model the underlying mesh models created for Reach.

Overall I've enjoyed what I've played so far on Halo 4 but at the same point I'm disappointed with some of the things I've noticed. I'm up for progression but some of the "progression" is retconning the absolute trout of the predecessor games.