Amazon:

Elemental Bow/Javalin skills have been buffed, poison benefiting the most
Multi-shot will now do 3/4 normal damage again as in its original form
Less range on guided arrow
Melee spear skills buffed

Sorceress:

Most skills slightly buffed
static field has its range reduced.

Necromancer:

Poison Strike buffed
Bone armor AC buffed
Bone skills buffed in damage
Less range on bone spirit
Skelemages damage buffed

Paladins:

Smite will no longer be affected attack speed
Sacrafice buffed
Blessed hammers damage slightly decreased

Druids:

Elemental melee skills buffed
Wind skills buffed
Armageddon buffed

Assassin:

Kick skills buffed
Martial arts skills buffed
Trap skills buffed
Reduced HP gain per level
Increased HP gain per VIT

Items:

Sszak string no longer will kill mercs
Higher end staves have been improved
Ber runes now give 4% CB instead of 5%
Skiller charms will be more rare and are now a lvl 80 item with a lvl 80 req
All zod runewords have been buffed

Mercs:

Act 1 physical nerf will no longer gain levels in the multi-shot skill through leveling up. Only way to raise it will be through + to skill items.

Difficulty:

Curses/Freezing duration penalty increased in hell difficulty
Diablo, Izual, Whitedragon, Hellforge Dragon, Chimera are tougher
Berserkers now appear at the monastery gates and outer cloister
Bosses in general will be slightly more durable and an increased chance to block

Lag:

Laggy bosses Glasya, Hellforge dragon and Moloch have had their laggyness reduced