This update should overhaul mainly the combat system, but of course a lot of other features as well.
If you are a fan of dual wielding weapons then you will be in Heaven. Because right now it's possible to equip two items at the same time and use them independently. You can now light the way with a torch in your hand and still be able to defend yourself with a sword in the other hand. Of course with this patch comes also different moves and ways of attacking!
There are many other things you should check out. For example new attribute system, skeletons can trap horses, 13 new blocks, new particles, attack strength mechanic and of course changes to the existing game. New harder AI for skeletons, visible status effects on the main screen, sword blocking removed and much, much more.
See the complete list at Minecraft Gamepadia.