edit: just remembered they have a referral system, should you be interested: http://www.fastmail.com/?STKI=13352501
On top of all of that, they actively contribute to open source projects such as Cyrus.
However, I'm using an IMAP box on Gandi.net and a domain purchased elsewhere and that is it. I refuse to use any services tied to a single company any more.
This change has given me a lot of headspace for other things.
It also comes with 10 minute turnaround time on phone support. You get a little popup asking if everything is okay and if you want to receive a call for support when you login to the admin interface.
I've been quite happy with it for the last three months.
I do have two-factor authentication after a scare.