I started using GPG seriously once the "easypg" integration landed in Emacs 23. When you open a .gpg file it prompts for your passphrase and decrypts transparently, and when saving a new .gpg file it prompts you with a list from which you can select recipients to encrypt to.

The integration with Emacs mail clients is fantastic too; just M-x mml-secure-sign or M-x mml-secure-encrypt when composing, and incoming messages with signatures are typically checked for you.

This totally changed the way I used GPG. (from "not at all" to "every day")