I just received my 150mm lens, and yes it is big, but we are all perfectionists that want the best image, right? I have to add the autofocus does seem extremely accurate. I spent the day performing the focus trim procedure for the first time, to make sure the lens would be as sharp as possible in autofocus mode. I learned a couple of important things.
Firstly, the lens was very close to being spot on; only a small adjustment was needed (and for my 80mm lens,zero adjustment- good job Phase One).
The amazing thing, however, is that when comparing autofocus images to my manual focused images, I learned that my ability to manually focus is not even close!!!! I only learned this because the tests were done with the lens wide open, and photographing a test target, which was then magnified at 100% in Capture One. This is quite a revelation to see that my manual focus ability did not even come close to the autofocus in accuracy- some images were in fact way off- the test target was a blur. I did the test with other lenses (80, 120mm) and the same results.
It is very surprising to think that all these years I used manual focus for landscape work, because I felt it was more accurate, and it may have been the opposite. My results were probably masked by the fact that I usually stopped down at least a few stops for depth of field.
Amazing.