Lots of interesting things shown thus far...
Adventures - Is replacing Grimoire cards and essentially are 10-15 minute missions where you accompny an NPC who tells you about the lore of the world. Upon completion you get given a map which leads to loot. Not sure how many there are, but there must be alot if want to keep the lore strong..I would imagine some will be linked too, if you recall The Book of Sorrow it was a long, highly detailed set of cards. Thatkind of detail needs to remain in this new system.
Weapon Mods - Unclear what these will be, but I think it will be more significant than just a skin/shader and will be an attachment(sight, extended mag, etc) or maybe a rune type system that buffs the weapon or changes how it works.
Exotics - The fw seen or implied to be have been interesting, the Gally inspired grenade launcher looks good. However, it is the Exotic armour that is pleasing me most. In D1 the exotic armour was very meh visually for the most, But in D2 I saw some Titan gauntlets with big bull like horns sticking out, it looked cool. Also saw a very ornate Warlock chest with big gold wings.
Lost Sectors - I love the fact that you can just go searching for them rather than being forced to do certain missions/activities in order to locate and access them.