Well to answer some questions, what I did was photograph a gallon plastic weed killer bottle that was about 45 feet away at the bottom of the yard. The bottle was a good subject as it has writing on it. My initial tests showed it to be a bit fuzzy at full aperture, with improvement with the lens shut down. On re-reviewing, it looks like the ground immediately behind it was sharper, leading me to wonder if the rattling rear element caused some erraticness in the precise plain of focus. Now the image is much sharper and compares with images shot with other Nikon lenses that I have (80-200 f4 and 35-135 f3.5/4.5). With none of the lenses is the small writing on the bottle legible, but the images with each lens are about as sharp as each other. Again, the test was done on an oldish digital camera (D200) which also introduces some limitations. My 35-135 produces razor sharp analog 8X10s so I am sure the 105 will now too.
The rattle was not significant, and the tightening involved an almost imperceptible turn of the element, but it makes quite a difference.