The differences are legion.
Bardic music is less flexible and more powerful in combat.
Diplomacy is now two skills: Taunt and Persuade.
Familiars are more powerful.
Parrying is now a skill, with many resulting differences.
Expertise is replaced by parrying.
Power Attack is an inflexible -5/+5 adjustment.
Dwarfs, gnomes, and halflings don't have reduced movements.
Discipline is now a skill that opposes special maneuvers and taunt.
Special maneuvers generally have a penalty to hit and are opposed by discipline, not by an attack roll.
Summoned critters last for 24 hours.
Hit points heal completely when resting.
Death costs 10% of your gold and 50 xp/level.
Any others?
Daniel