Snapshot 12w23b is here! Watch the video or red below for the changes!

Enchantment levels are slightly exponential again.
It now takes 825 Experience to reach level 30.
Added Ender Portal frame to creative inventory.
Half slabs are placeable on walls
Tripwire adjusted.
Tripwire is now activated by all entities, including arrows.
The max distance has been increased to 40 blocks.
Boats adjusted.
Boats can accelerate to faster than previous speeds.
Boats are now easier to control.
Wooden Pressure Plates detect arrows.
String placed down has a smaller black frame unless on TNT, leaves or pistons.
A lot of smaller changes and fixes.
Texture Packs that are in folders and not in a zip file are recognized as a texture pack.
Texture Packs image is displayed for folder based texture packs.
The player can now see the cracking effect on blocks when other players mine blocks in multiplayer.
Bug Fixes:
Pressing F no longer reloads chunks.
Fixed a bug when pistons pushed a wire.
NPC Villagers procreate again.
Mining a ore give now 3 times less experience orbs.
Weathers transitions are back.
Slime and Magma Cube jumping animations have been fixed.
Armor and Tool enchantments now show on multiplayer.
Notable Bugs: (Complete bug list):
In some cases when writing on a Sign and clicking done the text is deleted.
Repairing items using creative mode in the inventory crafting grid will duplicate the item.
Tripwire (String) can be placed on top of each other like any solid block.
Frequent null pointer exceptions in survival mode.