(author here)
I have the same angst about interface changes. I am so extremely dependent on being effective in gmail. If they ever force me to use one of the new interfaces of Gmail, it will be a new client for me to learn, thus i might as well learn a completely new client - like eg mutt.
> new interfaces of Gmail, it will be a new client for me to learn, thus i might as well learn a completely new client - like eg mutt
That seems sort of silly... Various gmail interface changes have annoyed some people, but they're quite small by comparison with the difference with an email client like mutt with a completely different model, and not just the UI model, but mail delivery, storage, backup, and spam-handling, not to mention the integration of gmail with a vast swath of other software.
Certainly mutt (and all the associated things that go with it) are better-liked by some people, but it most certainly isn't going to be easier to learn than new gmail UI for an existing gmail user. Not even close.
