the Disc does help, it will help lower contrast aka picture to a lower settings that does use lower power consumtion on CRT's and plasmas.
It will help with brightness level to get better detail in the dark areas of the picture.
plus help people turn down sharpness, turn of edge enhancments if possible.
and get you the best pre set color temp, like the warm setting.
but It will not get the color temp perfect, correct grayscale, gamma, and let you turn off edge, color, or black enhancments, etc.
As for the TV in BB that has the same settings in the user menu, this is wrong, the TVs in the store are set only in the service menu to show customers that most of the setting that need to be change are only in the service menu.
But in the customers home they use both menus to calibrate the TV set, it can get confusing because some TVs give you picture setting for every input within the user menu, but in some cases not the service menu, so it requires a great knowledge of TVs and TV make and models.
I have four disc from DVE, sound and Vision, monster, and avia.
Ive used all of them, but the ISF calibrator still fixed some problems with my TV when I got it calibrated that I couldnt do, not because I could get in the service menu, I looked up online to find out how, but once I got in the service menu I didnt have the right equipment to make the right ajustments.
hope this help