While fixing some major issues in the game, patch 1.4 seems to wreak havoc on quite a few textures in the game such as the Arcane Enchanter, Nightingale Armor, and Attunement Sphere but possesses no known harmful effect on the game itself at this time. This has been confirmed on all platforms.
PC This patch also brought new bugs, such as incorrectly duplicating and replacing items and favoriting bugs, such as having two improved weapons (same level, one-handed, and same name) not being able to be dual wielded if they are favorited, instead automatically unfavoriting one of these weapons when trying to equip both.
1.5  - March 30th, 2012 (PC), April 5th, 2012 (Xbox 360, PS3)
PS3 Although the screen will freeze the instant you are transitioning to "underwater-view", forcing you to restart your system.
This bug is fixed by quitting Skyrim, opening up the game data folder on the XMB and deleting the main "Skyrim" Item AND the game patch (update), This removes both items from your console but keeps all saves and any additional stuff like options intact. When you restart, you will have to re-install the game data and patch, but it is a minor setback to an otherwise potentially game breaking bug.
1.6 - May 24th, 2012 (PC - Beta), June 8th, 2012 (Xbox 360)
Mounted Combat - Skyrim now allows you to do melee and ranged combat while riding a horse
General stability and memory optimizations
General AI pathfinding optimizations and bug fixes
Optimizations and crash fixes for data leaks
Fixed rare crash with lighting
Fixed crashes related to loading and saving games
Fixed crash with summoned creatures/NPCs
Fixed rare issue where saves would be corrupted
Improved logic for when ranged kill cams are played
Fixed issue with ranged kill cams while killing a dragon
Fixed rare issue with certain ranged kill cams not playing properly
Fixed issue with nirnroot lighting not properly cleaning up
Fixed issue where bow damage was being calculated incorrectly
Fixed rare problem with werewolf kill moves would not finish animating properly
Fixed occasional issue where followers would disappear after player pays off a bounty after committing a crime
Fixed issue where certain creatures and NPCs would fail to respawn properly
Fixed rare issue with dialogue subtitles not displaying properly
Fixed issue with water appearing blurry when loading a saved game after creating a save underwater
360 Fixed issue where map cursor would occasionally disappear after closing a message box with Kinect enabled
360 Fixed rare issue with shouts only performing the first level and not other unlocked levels with Kinect enabled
360 Fixed issue where the shout buttons would stop working properly if users mashed LB and RB during cooldown with Kinect enabled
1.7 - July 30th, 2012 (PC), August 9th, 2012 (Xbox 360, PS3 in NA), August 27th, 2012 (PS3 Worldwide)
General memory and stability optimizations
Fixed crash related to new water shaders
Fixed rare crash related to dragon landings
Using Vampiric Grip and swimming no longer prevents swimming animation from playing afterwards
360 Fixed logic error with loading screens from add-ons
360 Improved recognition with Kinect voice commands
360 Fixed issue with Dawnguard Kinect-enabled dragon shouts for French, German, Italian and Spanish
PS3 Retroactively applies the previously skipped 1.6 update (Horse combat)
1.8 - November 1, 2012 (PC), November 26, 2012 (Xbox 360, PS3 in NA)
General memory and stability improvements
Fixed rare crash when using vampiric grip
Fixed issue where Arnleif and Sons Trading Company could become permanently locked
Fixed issue related to duplicate NPCs
Fixed rare issue where exterior door would not open properly
Fixed issue with horse animations
For PC, if you're on the quest A Cornered Rat, on the quest objective Talk to Esbern, he may not use his voice and you can kind of fix this by turning on subtitles. After he decides to let you in, the door may not open. To fix this, save the game, quit to Desktop, relaunch the game, go back to the save and he should open the door. He still may not use his voice though. After speaking to him, he may scramble around for a few things. Do not worry though, if he is searching in his chest, exit the warrens, come back and make sure he is scrambling for something on his table. Proceed to talk to him and tell him that you and he must move.
1.9 (Xbox 360 and PlayStation 3) April 21st, 2013(PC) March 20
Legendary difficulty setting
Legendary Skills – Skills of 100 can be made Legendary. This will reset the skill to 15, return its Perks and allow the skill to affect leveling again. This effectively removes the overall level cap.
General memory and stability improvements
Fixed issue with quest scripts that were not shutting down properly
Companions will equip better weapons and armor if given to them
Placing an unread Oghma Infinium on a bookshelf in the player’s house no longer allows the book to be reused again
Adjusted dialogue priority to improve chances of hearing more combat dialogue from certain NPC enemies
Fixed issue with falling damage on high difficulty levels
Fixed bad collision on certain clutter objects
Fixed rare instance of couriers who would appear only dressed in a hat
PS3 The game may freeze if a spell makes too much noise, if there are too many footsteps, when pausing, when starting a conversation, just when an attack is about to connect, or after being slain by a power attack.
360 "Dead Man's Respite" Puzzle door circles can not be activated, when not on a quest, causing the player to be trapped with no way out.
PC Skyrim will shut off the monitor of your system if you are running an AMD/ATI graphics card. It requires a hard restart of the PC with its attendant risks. Bethesda has not confirmed this bug or a fix for it.
PC Sometimes, it's impossible to finish the Dragonborn Main Questline. (Miraak's battle bugs)
360 Legendary Skills: the Lock pick skill will not work after the skill is reset. The skill will only increase when a lock pick breaks, not when a lock has been successfully picked.