The problem with Japanese struts and shocks is, and has always been, in my opinion, a problem with excessive high speed damping. For the performance you get, you always have a harsher ride than necessary. A good example is to compare almost all of the Japanese aftermarket struts for our cars to the German struts. The KWs, for example, perform better than almost any of the Japanese struts and feel more comfortable! True, it's a combination of factors including the fact that lots of the Japanese coilovers include too-stiff springs, relative to the performance you get, but a big part of the difference in _feel_ is the high speed compression damping.
My 2005 STi has two problems. (1) the struts clunk. Bilstein has decades of experience building inverted struts and I've never heard of anyone complaining that they clunk. Many people over the decade or more that Subaru has used KYB inverted struts, have complained about the clunk. I don't know why my car clunks, but I do know that no fix implemented so far works to remove the clunk.
And (2), the STi's shocks are valved for too much high speed compression damping. Every bump in the road bounces me into the air. The spring rates are SOFT! 200 pound springs on a nearly 1:1 motion ratio strut system should feel soft and compliant. Certainly, when you feel an STi running 3-400 pound springs on good coilovers, you don't get bounced around nearly as much. Why? Because the high speed compression damping is less and the wheels are allowed to move up and down and follow the road and the springs can do their job properly.
What's the problem with "proper" high speed compression damping? It doesn't feel as ricey / "sporty" in the minds of consumers.
It would be AWESOME if Subaru would spec the same or slightly stiffer springs for the new STI and then properly match the struts to the springs, without going overboard on the high speed compression damping. Then the car would handle better and feel more "compliant" / comfortable.
Just in my opinion, of course.