They are gnome/svirf only and if you exceed a very low weight limit they break. The opportunity cost to using them is generally restricting your inventory to a couple pieces of food, a canteen, and maybe one backup weapon.
So you get to avoid trip and quicksand at the cost of being able to stockpile preps and have a variety of weapons to either use multiple specs or exploit vulns.
It’s not a bad trade off for villagers and their enhanced melee (resist and potentially deathblow) but anyone else would be better off just grabbing fly potions with the exception of situations where you face dispel plus trip gank or quicksand.
Being able to use cabal pits to dump gear while you fly can sort of help let you straddle the line but then you spend a lot of time dumping and getting which nukes your mobility and flexibility.
Honestly I think they are one of the well balanced pieces of gear because they do something cool but you really need to pay an opportunity cost to use it that is meaningful.