It was a pretty 'meh' game, generally positive but not brilliant. For any other developer it would have been a success, in terms of Bioware's track record it was a massive flop.
Personally, I got sick of the setting before I even started. The reasons for that are specific to me though - I was living in China then and all the games made there are set in similar time periods with similar themes, and half the tv shows on local channels were also historical dramas and my dad used to watch those non-stop for some reason. Jade Empire seemed to include every freakin' Chinese stereotype I could think of, kind of turned me off.
Add to that, the combat was fun but a little too easy. Once you get that one fighting style that stuns your enemy, that's pretty much it as far as difficulty goes (well except, for group fights against higher-level enemies). The only remaining challenge was using combos to finish every fight with all stat bars full. The story (separate from the setting) was pretty good and I honestly didn't see the twist coming even though it was obvious in retrospect (they always are).
Oh yeah, and that minigame with the flyer was stupid as all hell and I'm glad Bioware has stopped doing that type of crap (it was also the fly in the ointment that was KOTOR).