Thanks to everyone for the replies! Now to add my own experience so far.... It's not much experience, lol! I've only gotten in 2 games of AoS 3rd edition and in both games things went more or less as normal (since the majority of the core gameplay rules are the same), but neither myself nor the people I was playing with were good at remembering all the new things to do in each phase.
We basically forgot about Heroic Actions and Monstrous Rampages the entire game. We only remembered to pick Battle Tactics once or twice, but we at least remembered the Grand Strategy
Smaller unit sizes are fine, unit coherency is not. It's a terrible rule and it should go die in the Warp

I 100% agree with the sentiment that the monster-focused rules were just made to push sales of a new model type since hordes were the way to go in 2e and monsters didn't stand a chance against 40 units shooting them to pieces or shredding them in melee through sheer weight of attacks. I personally think this change was almost entirely due to three factors: 1: Sons of Behemat weren't good when released in 2e, and GW really wanted to sell those big, $200 single models. 2: They also wanted to push sales of their "god models" like Teclis, Alarielle, Archaon, Kragnos, etc. (except, of course, Kroak, who had to be nerfed despite getting a new model since he was the single most complained about unit at the end of 2e). And 3: They wanted to create an illusion of a lower bar of entry by pushing the idea that you now had to buy fewer models to get a competitive army. But this doesn't really seem to be actually the case, as now you have to buy more of the expensive mega heroes or elite units like Varanguard, Dracothian Guard, Stegadons, etc. to get a competitive army, and the cost of those models is going up.
This is speculation, but what I don't like the sound of going forward is this "Seasons of War" idea, or whatever it's called, where they focus on a new Realm of Battle each year. Presumably, this will mean a shift in the meta around what unit types and armies are going to have an advantage each year, in the hopes of getting the super-fans and meta-chasers to change up their army, if not just buy an entirely new army, every year. I would much rather them at least try to balance their game. But instead, they seem to be leaning toward the League of Legends approach of "let's just change the game constantly to force people to use different characters" This practice is rather scummy even for video games based on microtransactions, I think it's downright nasty for a game that requires physical toys that can cost $50-$100+ for a single model and also have to be assembled and painted by hand.
But on the good side, monster buffs were needed and are much appreciated. While I agree with
@Erta Wanderer that I like the feel of larger armies duking it out, they really needed to find a way to make monsters more usable. I would have preferred simply bigger monster buffs rather than kneecapping hordes, but like
@Killer Angel said the new edition feels like a "one step forward, one step back" approach most of the time.
I will say I actually like the addition of things like secondary objectives and more reactive command abilities. These are a step in the right direction and they make the game a lot more interesting since they keep both players engaged during each other's turns. They do take some extra work to remember, though.
While I personally hate the fact that battalions don't give very good bonuses anymore, I can agree with why they were removed. There were a few factions with battalions that were so broken it wasn't even funny (Tzeentch), and many with battalions that weren't even worth taking. Same with Realm artifacts, although in practice all they did was take away the Aetherquartz Broach and replace it with Amulet of Destiny, lol! I hope that they introduce some better artifacts when the battletomes start coming out.
The power creep for new units is real, though. Most good units are starting out with a 4+ save, and most heroes or tougher units are on a 3+ or even a 2+ save to begin with. So unless you have rend 3 or higher, you're often dealing with enemies that only take damage if they roll 1s. Not fun.
All in all, I don't hate it, but don't like it. Perhaps after I play more 3e games I'll get used to it as I get a better understanding of how the new gameplay works. But one thing I can say is I still love playing Thunder Lizards, and that hasn't changed with the new edition! Just give Saurus some love this time around, will you GW?