I've encounter two bugs so far, both in the same location. I backstabbed a guy, but instead of dying and falling to the ground, he fell up into the air and hovered before eventually getting up and attacking me again, only this time he appeared to be using some kind of god mode. Reload.
I shot another guard with an arrow for a one hit kill, but instead of being impaled on the wall like the last guy, the arrow began flying around the room in random directions, with the body rotating violently around it. Crazy.
As Pidesco mentioned, if you aren't interested in combat this isn't the game for you. Sure it has stealth, but it's not much compared to a dedicated stealth experience like Thief. Nor does it have the RPGness of Arx Fatalis.