[claudius]

> anyone can confirm that your email was signed (with many email clients), so there is value to using s/mime prior to all your contacts also using it.

Provided that they trust the people handing out these certificates – with PGP, they need a chain of trust to your key to verify that it is you, with S/MIME, they have to trust random third parties. Or do I miss something and you mean something else that is possible with S/MIME but not PGP?

[joshuak]

Right now if I send my Grandmother a signed email with s/mime she will see a little notice in her email client that says the message is signed and valid. If I send her an email with a PGP signature it will not.

This is because just like her browser the CA is trusted by her OS.