Mostly stuff you may have heard before, but a few new bits:
* Parry will mitigate 50% of the current and next hit, instead of being like dodge + parryhaste. Some subtleties not revealed here, like whether the second 50% mitigation is "lost" in a parry-miss or parry-parry sequence.
* Armor rebalancing will lead to less of a difference between cloth/leather/mail/plate.
* Block will specifically mitigate 30% of damage when it fires.
* Kings won't boost spirit. (So, spirit is basically no longer a core stat.)
* Caster weapons will still grant spell power; other items will (as we previous knew) only do so indirectly via Intellect.
* Weapon skills - gone. No need to learn them, no need to train them up.
* Reforging will allow you to replace one stat with 50% of another stat, with some restrictions. (Dunno if you can un-reforge an item, but the general idea is that this makes an item with +hit more useful if you're hit-capped.)
* Balance druids and elemental shaman will have a talent which converts spirit to hit, and will share spirit gear with resto druids and resto shaman.
* (From a follow-up) Haste will continue to speed up auto-attack as well as increase the physical DPS resource regeneration rate.
The post also contains a discussion of how existing gear will be re-itemized in 4.0.