My favorite new feature is slime blocks and the new fences and doors by far. My least favorites are the new enchantment system. I like the idea but I think it is poorly executed. I also hate the endmites because they are an unnecessary mob that are annoying and unoriginal. We needed at better ender mob. Tell me yours below ^_^
I don't like the fact that tnt minecart explosions wont work anymore. I had fun making my computer crash on single player worlds with it.