There might be a promise not to sell data, but you aren't doing any client/server encryption to prevent yourselves from reading it. If a government sent a request you couldn't deny, data could still be collected. Gmail has HTTPS, but everyone agrees that only protects from MITM attacks from the hacker in the coffee shop, not the one in the datacenter.
I'll stick with my current solution of lavabit (which encrypts all mails stored on their server) [2] and running my own roundcube instance for when I need webmail.
Does that really matter? I don't think the solution for people wanting to move off of GMail is to set up another company that stores your email.
What I'd love is a physical box I can plug in at home which stores my email and provides all the tools which GMail does (web/mobile apps, features, etc).
Even then, I'm not sure I'd switch. This is a tough nut to crack...but it's promising to see people trying. Hope something comes out of all the work going on in this space.