I’m very pleased with my Deuter day pack. Somehow, the frame and hip fins really do seem to transfer the load weight, so that you don’t notice what you are carrying. It also seems quite good at allowing air to circulate round the back. It has well-designed pockets and one side-web for easy access to a water bottle. It is slightly larger than most day sacks, which suits me as I can carry my camera and lens in addition to daily essentials.
I was surprised at how many explanatory YouTube videos there are about it and other packs.