Not really - BitBills have physical safeguards against the private key being read without leaving traces (you effectively have to cut the BitBill in half to read the private kay). I would never accept a wallet.dat from someone as payment because he might just as well have kept a copy. In fact, that's exactly the problem Bitcoin solves

Of course with BitBills you'd also have to trust the company creating them. When the value of a BitBill address becomes large enough, the risk of somebody having read it out through non-invasive means along the line might become too high as well - therefore I don't see BitBills as an effective means to let "millions of dollars or coin exchange hands".

I personally wouldn't trust a BitBill worth more than a few hundred USD from what I know about their current physical specifications.