I've been using mutt for just over seven years—and I've been really happy with it—but changing to Mac OS X has made me much more GUI happy since the GUI actually works on a Mac. So I'm routing all mail to Gmail and POP it over SSL from there with Mail.app (with the GPGMail plugin).
The fact that I can also send email through Gmail over SSL and never send my passphrase in
cleartext is the reason I even considered doing this. That, and the fact
that it's now possible to use
as sender makes it an easy decision.
So now my email is completely at the mercy of Google, but if they ever start to do nasty things it's less than two minutes of work and I'm back to using mutt. I can live with that.