darkSpyro

I thought the teammate AI was alright. My teammates split up and engaged enemies from both sides successfully without me having to command them all the time, but they did have some trouble with prioritizing their targets. They also healed me well, and for some reason the enemy AI didn't seem to focus on my teammates at all while they were doing it. The only enemy that I constantly had to deal with all by myself was the Warden Eternal, because the AI couldn't dodge his melee attacks at all.

I played on Heroic, BTW. But I don't think that affects the teammate AI.

The gameplay in general was amazing, and it really felt like a Halo game even with all the new tricks on the table. I especially liked the significant reduction in aim assist and the added mobility. The covenant carbine is still my favorite weapon, but the new SMG gets my love as well.

Story wise, it couldn't have been much better.
The ending was just perfect. Since the ending of Halo 3 I've wanted to see the whole crew together again, and now it's even bigger than it used to be. Also, if that is not a great setting for future Halo games then I don't know what is.
Locke is an OK character, and the fact that the newer spartans are so much more social than the old Spartan II's is a nice contrast. They seemed to know what they were doing by keeping Master Chief in the focus, instead of forcing Locke as the #1 guy. A lot of fans wouldn't have liked that at all, including me.
I was terrified that the Arbiter was going to die, and I'm so relieved that that didn't happen. Also, there was the first female sagheili ever in a Halo campaign. That was cool, even though we didn't get to actually meet her face to face.
I knew that Cortana was still alive so that didn't surprise me at all, but her effectively becoming a villain was something that I didn't expect. I loved it nonetheless, since now Chief is going to face an even bigger challenge of fighting his old friend, whom he still kinda considers his friend.
Also, I really liked the fact that they didn't just make her a rampant, crazy AI, but instead they gave her logical reasons for doing what she is doing. That makes her plan so much more interesting.
She was also super hot, which actually seems rather out of place, but I'm not complaining.

I do wonder why they tried to market the game with the idea of an "epic-scale sci-fi manhunt" so much, when the "hunt" (if it could even be called that) only really lasted for a couple of levels. It just kinda baffled me how Chief and Locke made nice so quickly in the end, seeing as how tons of marketing stuff suggested that Chief had been branded a traitor and a villain. None of that is ever mentioned in the game, not once. By my knowledge all of that stuff (the events of #HunttheTruth, etc.) happened in the time between the Meridian and the Sangheilios missions, which the game just skips altogether.
I dunno, I guess they were just trying to keep up the suspense, but still, not even a cutscene?

I wish we could've played as Blue Team more, but that's a minor issue really. Also, a couple of Fireteam Osiris' levels seemed really drawn out to me, like they were originally meant to be shorter and then extended for some reason.

All in all a great campaign. I haven't yet explored the MP much, but I'll post my thoughts here when I do. For now I'll just say that the REQ system has the potential to be a good thing, but it also has the potential to be really infuriating, depending on what randomly generated stuff you happen to get.
It has a huge emphasis on Warzone, which I don't think I'll be playing much (not intially at least), so I hope that won't make it suck for me.
As far as I know the loadout system is for Warzone only (which is good, I don't like loadouts in my arena MP) which means that 90% of the stuff you get from REQ packs will be completely useless to you if you don't play Warzone (which is definitely not good).

And lastly, less customization options is always the worst, and I really don't understand the logic behind that choice. It sucks balls, but at least we have loads of helmet and armor variants as a result.