The math definitely adds up. In the topic about it we discussed the math heavily.
No. Then I wouldn't know who screwed me. At least I know where Mike C (Casc..us) lives.
This on the other hand is still a valid point.
But you do bring up a good point. Even though you no longer have to worry about the private key ever even having been calculated anywhere by anyone, you do have to trust two entities to properly put the two key pairs on to the item and at least one entity to have properly added the two public keys together.
You can verify that there is coinage on the address listed on the coin though couldn't you? I think that casascius's physical Bitcoins have the BTC address that the money was sent to on them. If they don't, I know that BitBills do.