It appears to me that Canon is compromising by sacrificing properties that can be fixed by in-camera software, or in post processing for properties that cannot. They seem to be giving priority to center, corner and edge sharpness and to eliminating chromatic abberation. Distortion at the wide end or long end can be fixed by software, while sharpness and LOCA's cannot.
How can lack of IS be "fixed" by in-camera software or in post-processing? You could just say use a tripod, but then I'm not sure why Canon would make a MKII of this lens if the first one does so well? I know I can't be naive and think Canon hasn't been listening to those of us who want IS in a lens, or better ISO performance in a body, but at the same time it seems like they dropped the ball on this one.
I'm sure it'll cost more than the MKI with maybe a small %age increase in IQ that probably won't be worth it for most people. IS on the other hand would've been a fantastic feature to have (along with the improvements you suggest). That would given people who have been waiting a long time for this lens a real reason to upgrade.