Pros: It is not a card trick. Can carry with you. Can be repeated. Good ad hoc. Nobody can
possibly figure it out.
Cons: Few people carry coins, so provide your own. It takes a long
time to roll out to the finish. While it can be repeated, keep in mind it is a binomial answer (H
or T). So you may have to spruce it up be offering a reward if you get it wrong. And everybody
will ask you to do it again, so the shock value is diminished.