Well, for starters, I don't like that they have designed the new compose like a larger chat window. I prefer the compose not be a modal or window. I want my formatting above my message, right under the subject line. Perhaps, when compose is click a compose tab activates with full view on page compose form.

...and if they want improve auto save, give me a history diff every time it auto saves just incase I want to revert to previous version. This would be helpful for those times auto save kicks in just after you deleted a sentence or paragraph you're rethinking. Once message is sent, edit history can be removed.