It changed a good bit actually. You always gain 4 points in a stat (other than Luck) when you choose to level it, instead of it depending on how many related skills you raised since your last level. Fatigue is no longer part of the melee damage calculation, which means you can spam attacks without reducing your damage, but magic effects that raise your maximum Fatigue no longer give a damage bonus. Agility no longer affects your chance to be flinched when hit. The way difficulty settings are implemented changed from a slider to four set difficulties, and a bunch of enemies that were really tanky or had damage that was stronger than expected for their tier got nerfed. Also the new combat animations affect attack timing and weapon reach. There's definitely some other stuff I'm forgetting, too.