Bill Houghton, Sebastopol, CA
They look pretty neat. I've got some of the older quick-grip, from before Irwin bought the company that originated the design (not sure of that history; it could be someone else bought the original company and then Irwin absorbed that company...). I find they're mainly helpful for holding boards I'm cutting. When I want actual clamping, F- or C-clamps (depending on the size of the work) are my preference.

But these, and some of the other designs in this thread, may be superior to what I've got.