I've been bouncing between playing Destiny and Destiny 2 most of the week, and I'm super excited about basically every change I've noticed.
The biggest one for me, which I haven't seen discussed, has to be encounter design for the strike. To be fair to those having discussions, one beta strike probably isn't a large enough sample to draw meaningful conclusions from, but I love the change so much I gotta write it down somewhere.
There weren't any scarab fights. No ten to twenty minute fights, where you're hiding behind cover, avoiding one-shot kills, reviving teammates, and relying on spawns of add waves to refill your ammo. (Which you will run out of several times over, just unloading into a giant, bullet sponge.) In Destiny one these were all over the place. It wasn't interesting, after the first 10 seconds of "oh wow!" shock, the fights were slow, repetitive, and boring. They didn't challenge players, they just ate time.
Again, just one strike is hard to celebrate, as they didn't exist in every single mission in the first game, but the boss lends some insight into possible changes on this front. You could trade blows with it. It wasn't "oh, the boss is looking at me, or charging it's weapon, if I don't take cover I die now." It did chip damage. (Well, chip suggest small amounts, and it was fairly heavy.) You could shoot at it while it was shooting at you. You needed to take cover, and the adds were now a complication to how and where you took cover, and target prioritization, instead of super and ammo regeneration mechanics. They had to die so you could heal up, and had safe spaces.
It just... struck me as a vast improvement. The boss also died in a reasonable amount of time. It wasn't "Hey, don't mess up badly for twenty minutes." it was "Here's the target, here's more targets, don't all die at the same time, the more shooting you do, the faster this goes, we'll all be out of here one way or the other in five or so minutes."
I also really like the changes made to weapon slots, weapon types, and ability charge rates.
The sniper always felt like an awkward secondary weapon, because it was that special use, super hard hitting, not really traditional mid-short range combat weapon, like the rest. It functioned like a super most of the times you used it, you just got to use it all the time for whatever reason. Even as someone who had one slotted almost 100% of the time, it just makes more sense to me as a heavy weapon, and being free to have a scout rifle and a handcannon, or a scout rifle and an auto-rifle is really nice. It makes needing to swap between primary and secondary far less painful, and helps with the feeling of being able to fine-tune play style, and pick situations where similarly powerful weapons are slightly better for one situation or another.
Ammo did feel a bit on the scarce side of things, but I think I only ever ran out once, and it was as the last boss was doing a 2-3% health left enrage charge at us.
Finally, I did some PvP, which felt pretty good.
In the first game, I did a few matches for quests, and hated it. Everyone was sliding around on the ground with shotguns, killing me before I could react, or taking my head off with a sniper rifle before I knew the map.
This time I felt like I had a much better chance to play until people got the heavy ammo, which is what heavy ammo should do, I think.
It wasn't too slow to feel sluggish or boring, but I felt like I always had a chance to return fire.
All in all, I'm rather excited for the game to come out. Pre-ordered on PC... now it's just a matter of waiting.