I love 1.9, theres new mobs, items such as the Shulker, arrows, shields, Glider and you can use TWO ARMS! But the thing I dont like about it is the golden apple changes, the reload for hitting, armour changes and the new command blocks. I only hate the new command blocks because people are using them in maps such as the repeat command block, because it saves time on redstone. But if you have 10's/100's of repeat command blocks always on active, it lags you out, and OptiFine cannot save you.