Minecraft wiki entry for Development_versions, associated text: Better management.
The pick block action now works on blocks that are represented as items in the inventory (E.g.: repeater, redstone dust, and tripwire).
Pressing the 1-9 hotkeys while hovering over an item will put that item into the corresponding hotbar slot.
If there is already an item in the assigned hotbar slot, the hotbar item and the selected item swap position.
When in creative inventory, a full stack of that item will be transferred to that hotbar slot.
In creative mode, players can now shift-click items between the hotbar and the survival inventory.
The left-click action will no longer open doors, pull levers, push buttons or open trapdoors.
When in creative mode, pick block on an item will pick up a stack of that item.