The Redstone update will finally be there. This means much more interesting features, but it also means a time where most of your favourite servers won’t be upgraded yet for a while, so you will need to switch between version 1.4.7 and 1.5.
This update is primarily focused on Redstone circuitry and functionality but also comes with a lot of general bugfixes and generally improves performance. They reduced some lag that came from the graphics engine, the lightning generation and the way the server (or client-server) communicates with the client.
You can now already download the pre-release, for if you cannot wait, or somewhere tomorrow you will be able to update your client through the launcher. Note that if you are playing mostly on a (craftbukkit) server, you better not upgrade just yet.. or minimal take a backup of your 1.4.7 minecraft.jar just so that you can switch back to play on your favourite server.
Note also that if you have installed HD textures and other mods, they will be wiped by upgrading to the newer version.
Having said that, here’s the change log:
Added Redstone Comparator (used in Redstone logic)
Added Hopper (collects items and moves them to containers)
Added Dropper (similar to Dispensers, but always drops the item)
Added Activator Rail (activates TNT Minecarts)
Added Daylight Sensor
Added Trapped Chest
Added Weighed Pressure Plate
Added Block of Redstone
Added Nether Brick (item)
Added Nether Quartz and ore
Added Block of Quartz, with half blocks and chiseled variants
New command: /scoreboard
New command: /effect
Containers and mobs can have custom names
Inventory management has been changed, for example you can drag-place items over slots
Texture packs now have separate images for each block and item, and can have animations
Nether Quartz Ore now spawns in the Nether
Smooth lighting now has three settings (none, minimal, maximum)
More detailed death messages
Some hostile mobs now are harder in Hard difficulty
Many, many, bug fixes
Keep on gaming!