This version basically brings major change on gameplay of Minecraft. This game its mostly based for Java 6 and Java 5 has been avoided.
Now required version of Open GL would be 2.0 (instead of 1.2 and 1.3 for previous versions).
A new launcher who support these kind of files will be released soon and we will upload it as soon it`s became public
A note from Mojang says that it would take few more weeks for everything to be completed and launcher to be released.
Features which have been added to offline version of 1.6 are:
1. Horses and other animals has been added
2. Hay bales on the sea water
4. Carpets are now available
5. Respiration mode now helps much better for work underwater.
Proceed to the link below to download the latest version (offline one) of 1.6
Minecraft Offline Download