Let me just say right out that this game is awsome, and is in many ways deserving of a 10, but there are a couple of minor things that keep it from reaching that plateau.
First off, there are way too many unnecessary invisible walls. Granted, this type of game is prone to that sort of thing, and often the invisible walls serve a useful purpose, but it just seems to me that you should be allowed to walk behind houses or walk up hills that lead to other areas unless there is a specific reason you shouldn't be able to. As I said, this only a minor problem that only slightly hinders gameplay.
Second, well the story is great, some of the characters in the game talk way to long for their intended purpose. For example, when you encounter Brave Hui in Tien's Landing she and Sagacious Zu( if he is accompenning you) will drag out a story line about a little girl which seems as if it could have been said in a few sentences instead of 5 minutes worth of boring dialouge.
These problems I spoke of are only minor incoviniences, and in no way should affect the decision to play Jade Empire. Overall I would say this game almost gets a 10, but do to these and a few other small annoiances I would give Jade Empire a 9.