I have used gpg, off an on, for several years now. I have always liked the ability to confirm that I was the one that actually sent an email, and the ability to send an email and know that the receipient is the only one that can read the email.
Originally when I started to use gpg, the only way to sign a message was to incude the text based signature. Then SMiME allowed the signature to be included as an attachment. The problem that I have had is to explain to people that I am sending the email to what the attachement is or what the text at the bottom of the message is.
I think that I will have to come up with a good description that I can put in the signature comment that can help explain what the signature is.