orihalcon I suggest seeing my comparison video comparing the Brand New Model F's to the original 4704s and Model M's - even though they are just the prototype units, they sound and feel in line with original Model F keyboards, though no two F's ever sound the same in my experience. It's on the ModelFkeyboards.com home page.
There are no other reviews just yet as the first production units will be manufactured in March and ship in April/May, and I am arranging a meeting in NYC for anyone interested in trying out the working F62 and F77 prototypes.
1391406 I stand by the build quality of the reproduction units as comparable to or better than the originals. Today's tolerances allow for even more accurate parts thanks to improvements in manufacturing since the 1980s. For the most critical part, the barrels, the factory guaranteed a tolerance range of less than one tenth of 1 mm without extra charge. Judging by my micrometer measurements of IBM's original parts, they were not able to approach those tolerances.
The spring force is matched to original IBM standards, as well as the other parts. You wouldn't realize how worn out and dull some of the originals are until you've typed on a newly made one