There is some discussion going on now in the Yahoo! QTR forum on linearization. Seems the QTR maker Roy Harrington and Jon Cone differ on what is linear. Maybe K7 is different than using 3-4 blacks and an RGB space. Roy seems to like the "perception" approach.
When I played with altering the curves, I could alter the shadows for more detail and keep the highlights lighter without making them go into middle tones so fast, somewhat like the S-curve in old darkroom work. Somehow the current thought is a straight line in digital, but it really depends on what you like and the inks and paper you use too.
I also like staying with a RGB space to add a tint to some shadows or highlights. Setting it to a gamma 2.2 in B&W seems to be limiting for any subsequent toning short of using a toned B&W inkset like K7. Sometimes I think we get too hung up in the perfection and exactness of making it linear with 50-256 steps and really isn't needed and 21 would suffice for a print. God help me if Ansel Adams came up with some 21 step Zone System.
Imho of course.
SG