Ish,
While I have not held a KZII, I don't really see it as a replacement to the TTKZ. Just like a BWM is not a replacement for a FBM... Who am I kidding? I'm just trying to justify buying a KZII. However, I think that the TTKZ's are going to get progressively harder to find as time goes on.
Additionally, I kind of justify the TTKZ as a piece of weight lifting equipment. Instead of pumping iron, I swing infi... That way, I can forget the gym membership and develop some killer guns at home.
When you buy a TTKZ, your buying more than a knife, you buying an experience.