I saw David do it once, at the booth, and then I found my hand reaching into my wallet for a C-note,
like I was Dr. Strangelove.
It just seems impossible that a 3-dimensional object (a folded
up bill or card) could somehow disappear into a plexiglass box. So this switch is just about as
close to 'invisible' as you can get.
Something that Losander says on his DVD applies here.
(And I paraphrase): "The trick is so good that even if you perform it poorly, it will still fool
people."
My only (small) critique is that I wish Regal would have gone over some different
ways to make a dollar vanish/switch a dollar for another. But if you've been in magic for more than
a week, you can figure out how to do this on your own. I just suspect Regal would have some great
tips on a bill/vanish switch.
But this is a small issue; the real issue is that Regal has
created a wonderful prop that's easy to use and very deceptive.