Quite a bit of complaints over at the elderscrolls.com about Oblivion's level scaling. If your not familiar with level scaling, it's when the mobs level with you. The pro is that you never out level an area's content, but the con is that all fights are disturbingly similar in their difficutly. There is a mod Oscuro's Oblivion Overhaul whose purpose is to remove level scaling. I'm hesitant to try it because of such a drastic alteration to game play.
I do like not worrying about out leveling areas, but at the same time, all the fights do seem about the same.
Supposedly Morrowind has level scaling but not to the same extent. Anyone with experience with both games care to comment?