Its too bad people are still having an issue as my DCt works so flawlessly and fast that I can't imagine faster performance from a transmission. WIth that said I drive mostly in manual mode which if you are experiencing the lag with D mode than the obvious fix is to drive in manual mode.
When I drive in D mode its always in D5 and to be realistic, its still an automatic mode and just like an auto tranny I expect there to be some delay between when I romp the pedal and when the thing engages. For me sometimes it will not downshift at all when I step on the pedal unless I go beyond the click-down point but that is uncommon.
I guess I adapt how I drive to a degree in D as when I want to accelerate, I step on the pedal a second before I know I want to go to kick down the gears, let off slightly and than go throttle when lower gear is engaged but this is different than lag.
Basically seems like some perform flawlessly and I can't image anything bettero ut there than this DCT.