This is the first time I am seriously considering leaving Gmail. Seems like a royal pain in the ass to switch though, since you don't "own" your email handle like you would a domain.
It's not so bad if you have a domain tied to the gmail account. I use myname@mydomain.com but point my MX records to use gmail for it. So switching for me basically means re-pointing to another mail service.
The only reason I use them is their spam filters are excellent. Otherwise I wouldn't.
Switching would be laborious if you're using @gmail, probably a case of looking at each unique domain name you've received an email from, logging in and switching addresses. Could be relatively methodical about it by taking a backup and then working down your inbox and deleting the emails from those recipients until you have nothing left. Could be a day job.
There is an option in gmail to forward your emails to another address if you wanted to do it over time.
With a bit of planning you can have a near seamless switch. The biggest pain point would be places where you have to reregister/change your email address, and you can avoid even that if you're fine with Google still getting to read all email that comes to that address.
It is a huge pain in the ass to switch, but the sooner you start transitioning to an email solution you control the sooner you'll be out of the tenuous position of depending on a free service that can be revoked at any time.
