I've jacked mine

under the rear tube bumper multiple times with no issue. I have a Expedition Imports front bumper that holds the Pinz up just fine, I'm not sure about the bumperettes strength.
Pinzinator and a couple of others raise a good point regarding stability. I have a stand that attatches to the bottom of the high-lift to make it more stable. However, nothing will be more stable than a good floor jack, or if changing the tire on flat ground, a decent bottle jack.
The main thing that the high-lift gives you is the flexibility of being able to use it on uneven ground with relative stability, while still being able to raise a vehicle high enough to change the tire.
BEWARE, do not stand directly over or in front of a high-lift handle while lifting or lowering the vehicle. I got a nasty concussion a few years ago when my old high lift wasn't completely engaged, and smacked me so hard in the side of the head I was knocked out in my garage for about 10 minutes.