Two factor authentication would be quite an uplift to Evernote. There is no other feature that is more important to me at this point. Google has done it in a very elegant way, that doesn't disable older devices and software versions from using the service, by use of special passwords that can be enabled and disabled one by one. Such an approach would allow Evernote to implement two factor authentication even though all platforms had not been updated yet. Or the user could simply choose to log in via Goggle ID ..?