Update - 1.6

[Mafios_X]

Added Nether support to multiplayer.
The client will ask minecraft.net if the current login is valid. If the server says “no”, a warning message appears in the client. You can still play the game even if this happens. [14]
Added craftable Maps.
Added trapdoors.
Added Tall Grass in some biomes.
Mushrooms now spreads (very) slowly.
Added server property view-distance. Sets the radius of terrain updates (in chunks) to send to the players. Range 3-15, default 10.
Added Dead Shrubs in Deserts.
Added allow-nether (set to true or false) in server.properties.
Blocks destroyed by other players in multiplayer now shows the breaking block particle effect.
Doors make sound for other players in multiplayer.
The record player now supports more than 15 different songs. No new songs/records were added, though.
Activated dispensers make sounds and trigger particles in multiplayer.
Players stuck in walls will slide towards the nearest gap if there is one.
Shift-clicking while crafting makes as much as possible and moves it straight to your inventory.
The blocks in the inventory and stats page got a new look.
Shift-clicking something in your inventory will push it directly in your hot bar and vice-versa.
Trying to sleep in the Nether causes the bed to explode.
Disabled Advanced OpenGL until bugs get fixed.
It’s no longer possible to build solid blocks on the top layer of the maps.
Booster tracks are now speedier.
Fire has been severely nerfed so it spreads slower, and doesn’t spread infinitely.
Seeds are now found in tall grass, using a hoe on the ground no longer drop seeds.
Compressed network traffic more aggressively.
Blocks that don’t change appearance when the data changes don’t send block updates when their data changes now.
Arrows shot by players can now be picked up by all players.
Minecarts and boats can go through portals, empty or occupied.
Block icons in inventory are much brighter than they were in 1.5 and before.
Water below a layer of source blocks no longer behaves like source blocks (making it extremely difficult to swim up in artificial lakes or in holes dug in the ocean floor, for example). (Possibly a bug?)

Bug Fixes:

Fixed running out of memory corrupting the current level.
Fixed the side textures of grass getting extra dark when mining them.
Fixed anaglyph 3d rendering mode having severe visual bugs.
Fixed the crash screen vanishing immediately.
Fixed not being able to target blocks when at x or z pos 1000.
Fixed the achievements screen messing up the sky color.
Fixed saving while sneaking dropping the player through the ground.
Fixed a system clock change messing up the game speed.
Fixed rain sounds not playing with fast graphics enabled.
Fixed hair and cloaks being rendered in the wrong locations on sneaking players.
Fixed the attack/swing animation not being applied to the armor layer.
Fixed player rotation not being loaded correctly when loading a saved game.
Fixed arrow physics, making them not get stuck midair when you open a door.
Fixed arrows hitting reeds, portals, and other non-solid blocks.
Fixed keybindings not getting saved properly under certain conditions.
Fixed the player not being able to sneak off lowered blocks like cacti.
Fixed a bug where the player could mine without swinging their arm.
Fixed boats placed on snow being placed too far up.
Fixed submerged boats rising very very fast.
Fixed sand dropping onto boats getting stuck in a falling animation.
Fixed a game crash when riding a vehicle or animal into the nether.
Fixed falling while riding not dealing damage to the rider.
Fixed buttons and levers too close to the player being impossible to use.
Fixed dispensers shooting through walls.
Fixed fire hurting through wall corners.
Fixed entities reaching water through wall corners.
Fixed placing doors next to cacti creating half-doors.
Fixed buttons and levers being placeable on leaves in “fast graphics” mode.
Fixed furnaces and dispensers not dropping their contents when destroyed.
Fixed dispensers biasing later slots.
Fixed farmland taking too long to dig.
Fixed tilling below some blocks being possible.
Fixed tilling the underside of blocks somehow working.
Fixed fences and stairs sometimes becoming invisible.
Fixed walking on top of fences not producing step sounds.
Fixed fire sometimes existing mid-air as an invisible block of pain.
Fixed fences and wooden stairs not being flammable.
Fixed fire effect on burning entities sometimes getting rendered in the wrong location.
Fixed fishing rod rendering being a bit lacking.
Fixed fishing rods being stackable.
Fixed mining glass hiding the clouds behind the glass.
Fixed rain falling through liquids.
Fixed items in glass blocks not getting ejected properly.
Fixed water interacting strangely with glass.
Fixed glass not blocking rain sound.
Fixed fences and signs preventing grass from growing.
Fixed rain and snow being incorrectly lit.
Fixed grass staying alive below stair blocks.
Fixed the achievement screen not pausing the game.
Fixed some screens breaking the sky tint color.
Fixed fullscreen mode switching causing mouse issues and screen closes.
Fixed chat messages surviving through game switches.
Fixed ice so it regenerates regardless of whether it’s snowing or not.
Fixed rain falling too slowly.
Fixed levers being placeable on weird locations.
Fixed floor levers sometimes not delivering a signal downwards.
Fixed floor levers sometimes not being removed when the floor is removed.
Fixed rail tiles sometimes not properly connecting to a new neighbor.
Fixed minecarts next to each other causing extreme velocities.
Fixed wolves not following their owner if the name has different caps.
Fixed creepers retaining charge level when they can’t see their target.
Fixed dying in the nether spawning new portals.
“Fixed” beds in the nether. example of the *fix*
Fixed inventory acting weird when portaling by making the portal close all screens.
Fixed wooden pressure plates being mined with pickaxes.
Fixed redstone repeaters having the wrong particles.
Fixed saplings being plantable through snow onto non-grass blocks.
Fixed ore density varying per quadrant from the center of the world.
Fixed dispenser graphics being one pixel off.
Fixed mushrooms spawning everywhere during nights.
Fixed animals only spawning near light during the night.
Fixed the multiplayer join screen input field being too short.
Fixed IPv6 addresses being parsed wrongly. To connect to a specific port in IPv6, use the format [1234:567::1]:25565.
Fixed network packets being sent unbuffered, causing huge amounts of packets being sent.
Fixed entity positions going out of synch sometimes. They get re-synched every 20 seconds now.
Fixed inventory icons not animating after being picked up in multiplayer.
Fixed mushroom soup not leaving a bowl in multiplayer.
Fixed entities above the map height limit becoming invisible.
Fixed healing not flashing the health bar in multiplayer.
Fixed arrows being animated really strangely in multiplayer.
Fixed arrows triggering too many entity move updates in multiplayer.
Fixed the compass not pointing at the spawn location in multiplayer. This does not seem to have been fixed example
Fixed fires being impossible to put out in multiplayer.
Fixed record players spawning client-side fake records in multiplayer.
Fixed records not playing for other players in multiplayer.
Fixed players spawning in the wrong location and quickly lerping to the correct location.
Fixed monsters not being visible for players with their difficulty set to peaceful.
Fixed pigs getting hit by lightning in multiplayer spawning client-side zombie pigmen.
Fixed loads of exploding TNT generating way too many particles, possibly crashing the client.
Fixed bonemeal use in multiplayer sometimes spawning fake client-side trees.
Fixed saplings sometimes spawning trees client-side in multiplayer.
Fixed weather sometimes changing client-side in multiplayer.
Fixed grasscolor.png and foliagecolor.png not being read from texture packs.
Fixed stats getting saved to different files in offline mode if the caps in the player name differ from the true spelling.
Fixed fireballs not being visible in multiplayer.
Fixed ghasts’ firing animation not being visible in multiplayer.
Fixed receiving more items than the maximum stack size sometimes causing an oversized stack in the inventory
Glowstone and Jack-o-lanterns recessed into a wall or other surface no longer have shadows cast on them by surrounding blocks when smooth lighting is enabled.
When breaking a minecart the player is currently riding in, the player no longer falls through the block the track is placed on.
Fire does not displace water anymore.

New Bugs:

Extreme lags on Linux and Windows multiplayer servers, the Minecraft process uses 100% of CPU as soon as the host is logged on. Others may log in via LAN, and wireless without lag. [15]
The frames per second of the client dropped considerably for some users. [16]
Items do not eject properly from any block, they will become buried if a block is placed over them. Must dig it back out to retrieve.
Items received from a Furnace sometimes have no stack number, items from the furnace can also be duplicated by right clicking.
Right clicking a Duplicated item from a furnace while the chest is open results in a crash.
Hatches Close through you even if standing at same level.
Tall Grass are off centered and can float off edges. (Possibly a feature?)
When looking at a map the indicator at the player's coordinates does not always point the correct direction. For example, when facing due North, South, East or West the marker will sometimes point slightly clockwise from the direction it should.
When pressing Q to drop a tool and re-collecting that tool, when you use it it'll break instantly. To avoid this temporarily place the tool in a chest after taking it.
watercolor.png doesn't do anything.
If you Shift-click to place items chest and the chest is full the screen will change to the "Saving Chunks" screen except there will be no loading bar and the text will be in a lighter shade of grey. The game will then crash and will flick to the error report before the screen goes black and you cannot do anything.
After death, any items dropped will give an infinite number of clone tools to the player when he/she attempts to pick them up (example: [17]).
Missing tooltips for Tall Grass and Dead Shrubs in Statistics menu.
Tall Grass looks grey in Statistics menu (because it's color depends on Dirt's block grass color).
Furnaces will sometimes eject all but the last item in every slot.
Upon logging into a world, the player receives half a heart of damage possibly due to spawning partially in the floor or ceiling, if indoors
An item bug was introduced where people could pickup items while their inventory is full. [18]
Some portals in SMP take the player to the same location in the nether, despite being quite distant from each other.
The screen from clicking "Save and quit to title" no longer has a progress bar.
Any music discs left in a jukebox before Beta 1.6 can not be ejected
Hatch textures are mirrored wrongly. [19]
Walking up or down stairs is much bumpier than previously (your viewpoint bouncing vertically).
Closed Trapdoors/Hatches let drops fall through.
Maps trying to view The Void will crash the game.
Glowstone now acts similarly to glass with regards to rails, torches, ladders, doors, etc. [20]