I don't mind respawn so much, if it makes sense. The Witcher made it work, at least. If I've cleared an area as part of a quest, then it should stay cleared. But in a forest or some such area it makes sense that some animals or creatures might still be around in the coming days. Sacred 1 made a horrible mess of respawn, because as soon as you traveled one screen over all the enemies had respawned, within seconds. This combined with scaled leveling made killing a huge pointless chore after a while.