I've owned both, and the mark I is well, OK. It is not real sharp in the corners, and the more you shift away from center, the more the corner shifts towards the center. Tilting was something I did not use much. If I was shooting a landscape and wanted the bushes and mountain in focus, I stopped down... I did shoot some cool tilt videos for that "miniature" effect.
On a crop camera this might be fine. on FF, i thought the results from my 24-105 shot at 24 (or 35, or...) then "fixed" in Photoshop to have straight lines, were just as sharp. If I was going to do that, why carry it?
The VII is decidedly better.