• Character can multiclass 4 classes.
• Ability Bonus cap increased to +18.
• Weapon buffing spells do not stack, only 1 can be active on same weapon at the same time.
• Casting a (defensive) spell doesn't cancel stealth mode. This supports sneak attacks with touch attack spells.
• Familiars and animal companions requires meat (any type will suffice) to be fed and thus healed via conversation.
• Immunity to mind-spells effects no longer grants immunity to paralysis and stun.
• Immunity to slow is also immunity to movement speed decrease effect.

• Added refillable potions. These potions must be equipped, they recharge their uses after rest.
• Helmet AC type is now Armor.
• Gloves are now equipped in main hand slot. Therefore unarmed monks do not lose item slot.
• Ranged weapons no longer uses ammunition.
• Bows and crossbows allows to equip new item type quiver into offhand. Quivers can have damage bonus and other defensive properties.

• Damage Resistance from items stacks
• Damage Resistance no longer exists for elemental damage, only physical. Feats granting elemental DR are now granting % immunity.
• Damage bonus of same type on a weapon now stacks.
• Regeneration from items is per 10 seconds now. Regeneration from other sources (feats, spells) is unchanged, thus still per 6 seconds.
• Items with AC Dodge bonus (as we have more than boots) doesn't stack, highest applies. Dodge AC from other sources stacks normally.
• Vampiric regeneration procs each hit, but will no longer work against variety of creatures without blood - skeletal undeads, constructs.
• Mighty property stacks on different items.

• 1 is not an automatic failure on saving throws anymore.
• Spellcraft bonus to saving throws works only against spells, not monster special abilities.
• Divine Grace and Dark Blessing feats bonus is now capped by class level. Paladin and Blackguard levels stacks for this purpose.
• Feats Dexterous Fortitude and Dexterous Will allows to use reflex save instead of fort or will.

• All spellcasters are now spontaneous and select spells known during level up.
• Spellcasters uses spell points to cast spells. The more spellpoints, the more spells they can cast.
• There are three types of spell points. Intelligence based spellcasters are using Arcana, Charisma based spellcasters are using Power and Wisdom based spellcasters are using Mana. If you combine two spellcasting classes of same casting ability, you can share the spellpoints.
• Casting a spell costs [spell level*2-1] spell points. Ie. 1st level spells costs 1 spellpoint, 2nd level spells costs 3 spellpoints etc.
• Number of uses will automatically recalculate anytime you cast any spell, rest, regain spellpoint etc. Additionally, a spellpoint bar will be shown next to the hitpoints bar left from the character portrait, that will visually show your spellpoint reserve.
• Items exists that grants bonus to specific spellpoints ie. Mana Bonus +20.
• Base spellpoints differs class to class, having high ability modifier also increases spellpoints of specific type.

This means that not only are all casters are spontaneous casters, all classes can now substitute “higher spell slot” for “lower spell slot”. So if you have 100 mana, you can cast 100x 1st level spell if you want, or 14x 4th level spell.

More information here: Spell Points :: d20srd.org