My worst buy was a custom rucksack made too fit my back length. It had one alloy stave which dug in my back at the base of the spine when loaded. Was meant to be my lighter backpack at about 1kg for over 50 litres. It would absolutely kill me an hour into an overnighter even if loaded with only 9kg!! It also had hip belts attached right at the side which meant there was a triangular gap between your back, the sack of the back and the hipbelt. This meant the load transfer was not good and made the issue with the alloy stave even worse. Won't say the name though as it is a good company just I made the wrong decision to get it. I could go back and sort out the hipbelt issue as they had another person who had come back for that simple mod. Perhaps I could even get them to make a sleeve to take the two pivoted x shape staves from my other sack which is a little bigger volume perhaps and is infinitely more comfortable. Perhaps even get an additional strap added to the hipbelt and the back so that it pulls the sack in at the lower back above the hipbelt level like my other sack.
Anyyway I do think there are mods you can make for the bits of the sack that don;t work. So I guess its not too bad.
I also would add the mini trangia as I don;t think it works as well as I thought it should.
I do have others too.