Alright, it showed up today....
I haven't put it to the test yet... but man this thing is STOUT! It will actually clamp into the negative, below the surface it's mounted to, by almost an inch if you really want to adjust it that way. The hold-down arm is about 5/16" solid steel, very heavy duty. I have no doubt in my mind this will do what it says it will.
The foot is perfectly flat, doesn't have any teeth to bite and grip in like the chinese one I had before, but it may not need it. I can grind some in if I feel the need. It also doesn't come with the bolt to mount it. Just has a 5/16" plate with four small holes, and one 1/2" hole for a couple of mounting options.
It also has the more logical push down to release lever, than the ones on every vise grip I've owned, where you have to try to squeeze them, and frequently need a pair of pliers to unlock them :P No matter how tight I clamp this, I'm confident a quick tap with a hammer would pop it open.
I gotta pick up a grade 8 bolt at work tomorrow, then I'll clamp it up and see how it goes! I am entirely confident in its quality, however.