Hey hey hey! Snapshot time!
Changes since 1.4.5:
“What’s this? This doesn’t sound like a redstone update at all!”, you say. “Indeed,” we say. Thing is, we* suddenly decided we wanted to make sure that you have fireworks for New Year’s Eve, so we’re working in several parallel branches of the code now. One is for the 1.5 “Redstone Update,” and one is now for a 1.4.6 patch update. This update will be out before Christmas, and 1.5 will wait until January (or possibly February).
I would recommend backing up your old Minecraft.jar somewhere so that you can keep all of your current mods. You can do this by just copying Minecraft.jar and pasting it into another folder.
* The client now comes with both the client-side and the server-side JAR files. The file called “minecraft.jar” should be in your “.minecraft/bin” folder as usual, and the “minecraft_server.jar” file should be in a folder called “.minecraft/server”.
Credits: The Minecraft Team