You all want some spoilers for Destiny 2? I won't...lol
Without going into the story at all, the graphics are beautiful. Worlds seem a bit smaller, but made some nice upgrades to move around quickly (you can fast travel between safe places). It makes getting to public events MUCH faster (which you will want to do a lot of them).
Honestly haven't attempted a nightfall, but some buddies tried one and said it was brutal (granted they probably weren't high enough in light level yet).
Interesting Crucible maps and changes to the supers that really make it fun.
Some new exotics and quite a few old ones with tweaks to them. Multi Midi Tool for an example (as others) have a companion weapon with them. You get bonuses when both are equipped, so remember to read the legendary weapon bonuses carefully!! Haven't seen anything similar in armor yet, but there might be...