Just jumped onto this thread from a recent one I started on this subject. I don't seem to suffer (that I've noticed) from rev hang when easing off in gear or down shifting (when it may be an advantage), but up shifting I definatly get a lumpy change unless I wait for revs to drop.
Being a very new owner I was assuming it was an engine trait I would need to learn to live with, but after a technician at Krazy Horse my local dealer pointed out this was an established issue, I'm encouraged to have it sorted.
IF an ECU upgrade can be had, and as the OP of this thread suggests without emission or economy issues, then I want it. Will begrudgingly accept the extra 20 bhp if its necessary
FWIW this is image inside my fuse box. Central box is switch control board - ECU is underneath, so nothing to be seen.

In any case will be contacting my dealer.
ETA: Forgot to add the up change issue I have is very noticeable on the generally very light throttle I have been on an engine having covered only a few hundred miles, and at modest revs say around 3000 rpm. Concerned now having read a little more of this long thread, there may be worse to come