Minecraft has taken a big step towards becoming more like a game with a beginning and an end rather than just an endless open world sandbox of fun (or horror). The new Adventure Update 1.8 which went live today adds all sorts of new fun thing, and changes up some playing mechanics as well.
One of the most interesting changes is a new health/hunger meter. When your player's hunger meter is at full you will regenerate health slowly, but your hunger meter goes down the more you sprint. There are also new rivers that wind their way through the world, and dead mine shafts which are randomly generated similar to dungeons. You can grow melons and pumpkins now, and torches give off light while in your hand. Randomly generated villiages will also pop up, but no occupants just yet. Perhaps the most exciting addition are the new Endermen, which will gleefully eat your face off as soon as they spot you and you turn your back on them.
There are tons more updates in 1.8, but also many others will be released in steps. So time to dust off that pickaxe and get back to exploring!