Hi-Lifts have their uses, but they are inherently unstable. There is a reason why auto manufactures redesigned the good old Bumper Jack, then scrapped the whole idea for a bottle or scissors jack in the 80's.
Jacking up by the bumper causes the vehicle to become unstable. If you have a lifted vehicle with some travel on the suspension, you may not even be able to get a tire off the ground using a Hi-Lift anyway. I keep wood blocks and a Dodge Van bottle jack in the Jeep to change tires.
I have seen people work under them and I cringe knowing that thousands of pounds of vehicle are supported by a single point no larger than a dime, 30" in the air. They have to be constantly supervised to be safe. Even changing a tire on level dry ground can be an accident waiting to happen without a buddy to watch the jack; many motorists over the decades discovered that via the Hi-Lifts cousin, the Bumper Jack.
This is one of those tools that you keep around, and like any other tool, carries a certain risk in the use of it. Use it wisely and it will get you out of a jam, use it wrong and it can kill you dead. Never work under one, and never put any part of your body above the jack.
That said, I carry one. I have lifted myself off obstacles, moved the vehicle off trees (Lift and push routine), unseated tire beads to clean them out, changed a set of tires out of the rims, pulled posts and the handle makes a good ratchet handle extension in a pinch. I should get a couple of the "Old Man" accessories, like a sling for lifting these heavy wheels onto the Jeep
