Loot 2.0 : drops less, but the drops are better and more meaningful.
If for an act 3 run you get 275 rares and 1 legendary in Diablo 3, you'd get 83 rares and 6 legendaries in Reapers of Souls. Some of them smart drops.
Smart drops : items you drop have a chance to be tailored for your character (looking at what stats you have on your current items?)
Level cap : 60 -> 70 (new skills and runes for every classes)
New artisan : the Mystic. Can transmogrify items (combine the look of an item and the stats of another into a new item) or reroll affixes on rares and legendaries.