The problem I see with Original Sin (and the reason why I'd never plede 100+ $ to it as I've done with others) is that it doesn't have anything that sets it apart. This problem actually permeates all the Divinity's. There's some humour, some world interactivity, combat is some fun as is character building (huge number of skills but many balancing issues).
Uhm… DivDiv's gameplay was an amalgam of Ultima 7's cutesy NPCs and world interactivity with Diablo-esque combat and character building. What exactly is it that you find unique about the Divinity's?