I bought three of these, two for Strat clones, and one for an Affinity Tele. They have no issues at all, the base is strong, thick plastic that's not brittle. The arms are steel coated with a non-slip rubber that leaves no marks on headstocks.
The arms pivot freely, with a little more play than I like, but once a guitar's weight pushes them down, they don't move a bit. Unlike horseshoe hangers, you don't have to bend the steel in order to adjust it, it adjusts itself to any guitar, even a classical with its extra-wide neck.
The Tele does not rest perfectly vertical because of it very asymetrical headstock, I don't have that problem with String Wing hangers, but they cost four times as much, so the Gravity system is very OK.
Before I knew the Gravity hangers I crafted three do-it-yourself hangers, but now that I found these at less than 4¤ each, I don't bother with sawdust and sandpaper, I just buy them.