After much hinting, foreshadowing and teasing, the newest Minecraft snapshot is out, showing us at long last what the much vaunted "exploration update" has in store. The most exciting addition for this most recent update is the "shulker box", an item built out of the newly added shulker husks, that finally upgrades your storage capabilities. You can stuff the box full of whatever you want, and it keeps its inventory, even if you destroy the block, letting you use it as a sort of backpack. Players have wanted something like this for ages. Even if you're not a survival player, it has its uses as a decorative block or as a way to upgrade your storage system, so this is a very exciting change.
The other big addition is the Woodland Mansion, which is a procedurally generated dungeon that appears very rarely in wooded areas. The mansion is filled with tough new mobs that cast spells, summon baddies and attack you with weapons, making it very much an "end-game" destination (though if you're lucky enough to find one early it can give you a serious head start on your build).
Woodland Mansion shows that Mojang is getting more comfortable with their procedural generation — the mansion is a lot more detailed and complex than earlier structures — which means that we could be getting explorable dungeons or structures for every biome eventually (and not just igloos).
As a part of the Woodland Mansion addition, you can also now buy exploration maps from the new cartographer villager. These maps show you the location of the closest Ocean Monument or Woodland Mansion, allowing you to set up an expedition with an actual goal besides aimless wandering. This is more exciting because of what it might eventually allow, but it's still another tool in the explorer's toolbox.
For tinkerers, Mojang has finally added an Observer block (which has been in Pocket Edition for a while), a redstone contraption that updates based on the status of the block it is "observing". While this might not sound thrilling to everyone, it's opened up a whole new world of automated builds, including flying machines, transporters and farms.
In general, it's not as great of a change as it might seem because the block has been around for a while. But the best redstone contraptions are still on Java, and this addition adds another powerful tool for players who can already built immensely complicated and interesting machines in game.
Other additions include llamas, cursed items, ways to escape from The End and a useful console command. Exploration players will no doubt be happy, and there should be something for everyone to enjoy, but the big question is whether or not Mojang can continue to deliver updates with this level of content in a reasonable amount of time. In terms of exploration and progression, Minecraft is still pretty features-light when compared to games like Terraria and Starbound, so if Mojang wants to compete in that arena there's still a lot of work to do.