i've tried, and you seriously have a snowflake's chance in hell of convincing any "regular" users of email to bother with encryption, they always look at me like i'm some kind of tinfoil hat nutter.
Really? For some reason I guess I didn't see it on the list.
The only people I email back and forth with that have a GPG key are privacy aware people. Even in light of recent events; it's still very hard to convince people that they should be using encryption to protect their communications!
Email encryption, I think, has the social stigma of being associated with a paranoid state of mind when it really should be associated with the human right to privacy and protection people feel when they lock the door at night or set their house alarm system.
So, I encrypt my email whenever I'm sending to someone with a key. I sign important emails.