I would like respawns of some description. I value immersion above all, and in my game I keep wondering why everyone is going on about this undead plague that doesn't exist as I have killed them all. I also keep hearing about these marauding orcs.... I killed a few and never saw any again. I'm starting to wonder if all the NPCs are just lying to me!!
Not saying I want the same mobs respawning all the time, but after a certain amount of time, having a chance(based on a stat maybe) for some kind of mob to appear would enhance the game imo.