The ALICE pack design is a remnant of the 1960's era when body ergonomics and design were just not a consideration. Modern pack designs contour to the shape of the human back and hips and offer much better support. The ALICE pack design is woefully lacking in this era.
I have one. Its been sitting on the floor of my man cave for over 10 years. I have much better surplus packs from the desert dust ups that get used much more. I tried selling mine and had zero takers even at $25 for the pack and frame.