I hadn't played Diablo since guild wars 2 came out and then resubbing to WoW, but I recently got an itch to check out what they have changed since last I played.
The monster power system is amazing. It lets you set how hard you want the game to me. I was able to beat diablo on inferno on 2 characters and have been slowly farming in higher and higher monster power. I've found about 15 legendaries since playing for about a week. Most of the good, and a lot of them I actually equipped right away.