The risers some times don't want to stay together so if you clip the bottom during a step or something, could be an adventure but honestly, not an issue typically.
When you just HAVE to know exactly how much you are lifting. I do use this more often than I thought i ever would with a couple of my machines and loading dumbbells.
Never actually use this for its intended purpose. I put one on each of my SSB when I have stored in my Darko Anchor so that I don't clip my head. Necessity is the mother of all invention.