This mockup shows off the Folder Bar, what happens when you have no message selected, and the Download-In-Progress indicator.
The reason I've chosen to indicate download progress in this area is because this is where new mail appears and it would go hand-in-hand with a Twitter-style pull-to-refresh action.
I'm attempting to phase the menu button out of my apps completely. I think for a lot of apps it isn't really necessary to have any sort of menu system at all.
I Like the menu button, as it kind helps balance the two sides of the app a bit more. Having only the search on the right side makes it seem a bit more left heavy.