I've used PGP for ages and it did work pretty well up to version 9. Since then it has been too intrusive with the mail proxy approach and too many bugs. I didn't know what a pain PGP was until I stumbled onto Thawte's free x.509 certificates for encrypting and signing email. OS X supports these certificates nicely in mail, the address book and the keychain. The integration is nice and clean and the interface is just a couple of buttons to click if you want to sign and/or encrypt. I even tracked down a couple of Thawte notaries so my certificate is tied to me, instead of my email address, for even better security comfort. I'll keep PGP around to read my old emails and decrypt one folder with sensitive info inside. But I've decided to end my contributions to PGP efforts and go the x.509 route which is nicely integrated into OS X. Check out http://www.thawte.com/secure-email/personal-email-certificates/index.html# if signing and encrypting email takes care of your needs. Thawte's web page and process to get the certificate is cumbersome and a little confusing. They act like Macs don't exist, but once you get your own certificate installed, you will love the seamless integration compared to fighting with PGP.