Hrmmmm.. I like the idea.. I've played with PGP in years past, but always found that it was more complicated than worthwhile. I never had email that contained a deep dark secret, or even a sweet innocent one. The problem here is that gmail does not play nice, which defeats the purpose of being able to go from one machine to another. (Something to do with the name and machine time and the private code I would guess) These days, with Carnivore actively poking around in everyone's emails, I have revisited the idea that everyone's email should be sealed up, even if that means taking a little more time and responsibility than mindlessly clicking >send<
Another option out there, which I don't remember much about or who owns them, is Hushmail. They use PGP and is a webmail service which is a pretty good thing. How secure they are, I do not know.
[edited From Wikipedia: Zimmermann suggests that "online encrypted email storage" cannot be expected to provide a defence against a legal process, because government can "compel a service provider to cooperate". This is in contrast to "using encryption software on one's own computer", which is presumably a reference to his original PGP program and equivalent software.
This almost certainly will apply to any and all companies which you hand your information over to. ;)