Let me just run down my thoughts in a none formal format.
Assassinations are back, but I feel as though they definitely need to refine them. They look choppy, and they look too similar to Halo 4's, but I believe this will be more fleshed out by the time the game is shipped. Also, I got me that sword assassination
Spartan Charging is pretty damn satisfying, just making someone fly in the air even if you don't get the kill. Same thing with the ground pound. Charging has more of a use than the ground pound though, and both need to be used with caution and precision lest you be destroyed. The Thruster Pack is also MUCH better than it's predecessor. It is unbelievably useful for escaping a bad situation, getting to cover, or just getting that extra umph to reach a platform.
The ADS, not ADS, Aiming, whatever, is alright. I don't mind it. It made the AR a lot more useful for far away engagements which isn't as bad as I first thought. I can't aim the BR well, but that's even when I'm not aiming down the sites.
Breakout is a gametype I've wanted to see in Halo for a while now, a gamemode that is pretty much Warzone from Gears of War except with 4v4 instead of 5v5. One life rounds, no full shields, it's pretty fun.
I was never a fan of loadouts, don't know if they are gone entirely or not, but I appreciate the fair starts. Something that I welcome back most definitely. Although, I am a fan of AR (or SMG) starts over BR starts. BR starts changes the whole complexity and flow of a match into a way I like less than AR starts do.
The Hydra is a lock on Brute shot/Concussion rifle. No two ways about, but I cannot for the life of me aim the damn thing. It won't ever hit anyone unless I am a good 10 ft away, and aiming it at them to lock on, which of course I believe is it's gimmick. Firing from hip with that weapon seems useless unless I am right on top of someone.
The ranking system ****** me off, which is the first Halo ranking system to do so since Halo 3's "Lose and you lose XP, win and you gain XP" system. Probably because it is sort of the same thing gist as Halo 3's except sort of not. It makes me mad when I lose progress towards Onyx II or lose my Gold Rank because of losing. This gives more incentive to win instead of just slay. Which I would guess that's a good thing, but I'm glad SR is also back because I do like a good grind sometimes. Just hope it's way longer than Halo 4's SR system.
I'm still on the fence about the Graphics, I'm pretty sure once I see the Campaign's design and the look, I'll be more inclined to give judgment on it. From what I've seen it looks ok. Nothing that would blow me out of the water. The Blue Spartan's do look like Blue Spartans, same for the Red ones, for the first time in a while.
Next week they're doing forge maps, which one has a rocket launcher on it, which I'll love to get my hands on to see how it works. I definitely want to see the vehicle side of this game, but it looks like I won't see that until the release.
Overall, Really looking good so far to me though. There are things the beta can and will refine for the better later though.