Make no mistake, the Warhammer world is a frickin' dark place. Things might look fine on the surface, but at the end of the day, its all doomed to destruction at the hands of Chaos. Being an adventuring hero is often nothing more than a fast road to corruption, or if you're lucky, an early grave. Corruption is THE fastest way to power, bar none. Of course, there's the problem where you become nothing more than a sock puppet for the nightmarish beings of Chaos, but I still say that serving Slaanesh is a good career option!
That the most powerful combat career is based around a desire to die in combat really sums up the world for me. And I played the Doomstones saga through to its ending, with the GM choosing the "Warhammer Ending". That was...interesting.
What's different? Percentage system, and damage can pile up really fast, if it gets through your toughness and/or armour. Magic is points based, and makes you a magnet for witch hunters. And Chaos is drawn to you like moths to flame. Not surprising, considering that Daemons are nothing more than raw magic given an evil sentience.
I can't wait, especially is they update the Skaven and magic. I loves my Ratties.