What keeps Oblivion from being perfect isn't any particular flaw; there aren't any hideous load times, game-breaking quest issues, or horrifically difficult encounters. Instead, just like the slow regrowth of plants you've harvested is one little thing among the thousands that make the game magical, a few very intrinsic issues conspire to drag Oblivion down.

For example, the excellent A.I. means that when an NPC greets you with a custom piece of dialogue (such as a guard's warning) and then reverts to the standard options (like a guard's cheerful directions just after that warning) it's more jarring than the canned dialogue by itself. The more polished physics and graphics interaction for character movement across slopes and over terrain is smashed by horses that can four-wheel drive down mountains and be tacked (like a sailboat heading into the wind) up any slope. All of the character models have exquisite levels of detail, from their shoes to their jewelry to their equipment, but they also all look like creepy next-gen mannequins -- not like people at all.