No, I don't really like Halo 4. And this is generally speaking from playing on Heroic difficulty or higher.
First, the campaign. Boring and kind of pointless. While yes there was some drama between Master Chief and Cortana, I didn't really empathise with her. She kind of shown that she should be put down pretty early on, and while I can understand MC's loyalty to her, when the angry ship captain wanted her gone. I had to agree. She seemed to be more of a liability then anything. (Besides she didn't really seem to be going crazy but just... erratically emotional.)
[[ Spoiler]] Though, kudos on killing her off. While it's a game late. (Should have happened in 3. She seriously wore out her welcome there) It was a enjoyable thing that makes me hopeful for the next game. Maybe we get to see some other people who are interesting or at least enjoyable. Maybe some friendly Elites or other Spartans (2, 3 or 4.)
The Didact. Next time you introduce a villain, give us time with him, don't give him the ability to just Force grab Master Chief and go, "Mwuahaha. I'm a jerk." This guy never really felt like a threat, or a villain, he just seemed to be some guy I should fight 'cause... racism? No, I should not have to go piss off to watch videos out of the game just to know what his deal is. (Or any of the other supporting cast.)
Weapons: While I liked some additions, mainly the SAW, the Promethean weapons should.. kind of be taken out entirely. The Binary Rifle is just a instant kill if someone looks at you wrong while using it. (Either in Campain, Ops, or Multi) The Incineration cannon is just a frustrating thing for the Knights to use, and the Suppresor and Lightrifle add nothing to the real dynamic of the weapons besides, maybe they're a little stronger? The Pulse grenades are generally useless, and though I like the boltshot, why give it a shotgun function when we've had maulers that did the same thing? (Brutes funner then Knights, by the way.)
Then there's the change of pace in the covenant weapons, most of their shots travel too quickly. Fuel Rods travel too fast when fired, giving too little time to try and evade, especially when so many Covenant seem to have them way too often it's just cheap difficulty. Another thing was allowing enemies to super combine you with needlers. You're already out numbered and out gunned, with enemies reacting a lot less to damage then before. For me, this was just a unnecessary change. Yeah, it makes the game more difficult in a way, but not in a good way. Just, more frustrating.
The covenant weapon thing is especially noticable in a banshee in campaign, where Grunts, Elites and Jackals can shoot one down pretty quickly. It, along with other things, ruin the flow of the gameplay, and really taking away from the experience.
Vehicles: It is far too easy to splatter someone. Ghost or Wraiths barely even need to move for a splatter, and a slow going warthog can do the same. They also seem generally weaker then even in reach.
Loadouts: I dislike this feature in the game, as I honestly don't think anyone should be able to start out with plasma grenades. While I do like it for Spartan Ops, having a standard weapon start or pre-chosen things Reach had would have been a preferred alternative for me.
AA: I dislike the removal of the bubble shield.
Connections: Whatever the problem is that makes it difficult to play Co-op campaign or spartan ops without one of the players getting input delay really, really ruins some of the enjoyment factors of this game. This also seems to put a off putting delay in multiplayer for myself at least where in some games it seems i'm a half second behind everyone else. (A problem which is pretty exclusive to Halo 4.)
Enemy A.I.: Too alert, too accurate, and too fast on reaction. Many times sneaking just doesn't seem to be an option, as if you get in ten feet on a elite or Knight, they know where you are, will usually turn around and severely damage or outright kill you with a melee attack. And, apparently can see through the invisibility AA which makes it sort of pointless in over half of the game.
You jump too high. No, I don't like it. Though this is just a personal gripe.
Also, customization unlocks. and the removal of level progress from campaign. Why have certain options limited only to extremely grindy and silly multiplayer commendations? Not everyone wants to play your multiplayer, and I don't think many people want to do several hundred assassinations for some armor they think looks neat (Especially if they're not that good.). Or use forerunner weapons in multiplayer just to get a stance. At least unlock these things for the general public later on down the line so not everyone has to try and grind for those things.
And, by the way, Spartan Ops online only? **** move. Should let those offline people at least have a Firefight mode if you're going to deny them the right to play part of the game they buy.
Also, whoever decided Knights should be able to teleport at will any time they want, with no discernable way to track their location change AND give them invincibility while doing this, should not be allowed to make enemies any more. Especially if you have them almost killed and they just cop out to some place you can't easily get too before they recharge their shields or something. Then give one of them a knockback shockwave type of attack, just doesn't give them any weakness besides simple brute force. Which is hard to deliver while solo on legendary. Basically, Knights are terrible enemies who are just too tedious to fight.