Reading through it seems a lot of my concerns have been voiced already but I assume quantity plays a role so here goes! Worth mentioning I’m from the Reach crowd and I still play on console.
Plasma pistol is useless, seems as if the heightened base movement speed of the game was not accounted for with its tracking. If it can’t hit players and can’t EMP vehicles, not sure what the point is, except maybe to make campaign harder (lol).
Assault rifle is stronger than I’m used to but I like that it can do something, alongside the sidekick which fulfills its name well. I’m very happy with these two as the standard weapon starts, and how they play with other scaled up small arms (BR, commando). Big kudos for that.
A lot of additions like the grapple and throwable fusion coils are very fun and go a long way towards diverse gameplay 
props there.
The Warthog is depressingly light and fragile. The electric car acceleration is fun but turns against itself very quickly with how easy it is to flip (similarly, the Warthog in the Title Update version of Reach is very susceptible to small arms fire. There are plenty of ways to deal with vehicles, let them do their work!) I would prefer a warthog that can go full gas most of the time and rely on good drifting (weight) rather than a stop-and-go zippy thing. It also should not be able to be destroyed by small amounts of small arms fire. Im not sure how the doomsday mechanic works; it seems fine as a way to warn the driver but sometimes it feels like some sort of “doomsday button” has been shot and I have to evacuate out of a warthog that isn’t even smoking yet. Not fun gameplay. I want vehicles to be worth driving, have a presence on the map, and to drive them into the ground till they explode.
On that note, the Ghost seems rather insane. I witnessed several splatters that were surely accidents - again the zippy electric movement (similar to the scaled up walking speed of the game now that I think about it) comes back to bite, as a motionless ghost can slide to the left suddenly and splatter someone they didn’t even know was there, teammate or otherwise. It can even compete with the Warthog head to head, which is ridiculous as the latter requires two people.
Staying on the topic, the base movement in general is very quick, the walk speed almost jarringly so. This produces a lot of downright unreadable situations, as even if you catch someone unaware (which happens a lot bc the motion tracker has a very small range comparatively) it can still be hard to line up a shot or get a back smack as they can pull their character left or right (or back!) at a moments notice, at best giving you away and at worst reversing the situation unintentionally. I assume my aim and the like will adapt with time but im not sure why the tuneup is necessary when sprint is a default ability everyone has. Increased movement means better strafing which means its even harder to use precision weapons (and the autos are better than ever).
Love the burst plasma weapon, the new plasma or storm rifle or whatever, very fun.
The Commando Rifle has a very light trigger, its a bit hard to single tap for me on console, not something I’ve experienced in a shooter before. Interesting gun though, not sure how I feel about it. Seems a bit all-in-one but haven’t played enough to know.
Will there be an option to not play with PC players? Halo is the original controller shooter and it feels bad to think I may have to go up against the precision of keyboard and mouse in a game with very low RNG on shots due to its controller origins. Its one thing to have to deal with it, another still to not even be sure its happening, since it could just be a cracked console player.
Echoing what others have said about post game screen and progression. I didn’t even recognize the progression issue because the end game screen was so temporal and frankly unrecognizable. A quick spread of players kills and deaths, and a tab through for medals would be nice, as would be xp for those medals.
Players holding objectives like flags should absolutely have get 1 hit kills lol.
Speaking of, melee in general seems absurdly strong. I doubt it’ll ever come back but I was very fond of Reach’s melee system: 1 hit drops shields, the next kills. Yes, this means that the melee itself has variable damage (a punch on 10% shields only cracks shields) but it also means the person on the receiving end knows if a punch will kill them. This new world of some amount of prior shield damage converting to a kill makes it really hard to know either way. And that some seems very small - a short AR burst and a punch does the trick. This again is another point in favor of automatics; punching to break shields and expose their head for a headshot is a wasted tactic in a world of bangbangbangpunch kills.
I haven’t gotten to play the maps much but the one that was available for BTB was well done. Had a lot of ways to play it, with none of them a clear best, leading to very diverse lines. The downside to this however is that its easy to feel lost or get flanked in ways you can’t well avoid. So while I enjoyed whatever that map was called, I also hope there are simpler more straightforward maps to keep things fresh, the way that Hemmorage in Reach had obvious cliffs to play around.
I did mess around in the smaller maps just to try them out, and the only negative thing that stood out to me was the design of whatever the small indoor black map is. The high points dominate large swaths of the map (and multiple objectives) and feature a prominent battle rifle spawn. Its a bit too have your cake and eat it too…historically power weapons are not located in the strongest places to use them, you have to get it and then get there. The combination is supposed to be the reward, not the starting point. Oh also, that desert map has a grav lift/airlift with an exit point that looks like an entry point. Slightly confusing.
There’s more I could say but I’m a bit tired, hopefully the feedback is mostly positive and yall are doing well thanks