Oh, I went through JE twice now. Playing once on each side. The first time around the game took roughly 32 hours to beat, although the vast majority of that was sitting through dialogue and actually listening to the voice acting. The second time around it only took me 22 hours to beat, as I already knew the solutions to the side quests and few "puzzles" (I use the term loosely) in the game, and I just skimmed the dialogue instead of listening to it.
It's a very fun game for any KoTOR fan. The fighting system is far superior to KoTORs due to the vast number of options you have.. but once you've played around with the combat system a bit, it's very easy to mix styles and cheese your way through fights without taking a hit. I was a little dissapointed at how easy it was to completely immobilize an enemy (including the bosses, who would have been VERY tough otherwise) and not get hit a single time.
The story was entertaining and relatively deep, albeit cliched. There was actually a good deal of pretty accurate Chinese mythology and geography applied to the game, although it's all under the guise of a created continent (the Jade Empire and Far East) for artistic license.
To be honest, I'd wait until it goes into the bargain bins or buy it used. Being a huge fan of asian culture/history, cheesy martial arts flicks, and KoTOR I may be a bit biased in my love for the game.. and I can certainly see how someone less enthusiastic about even one of those subjects could be annoyed at dropping $50 on a game as short as this. (Fable flashbacks, anyone?)