More than a week ago, I also made the switch to fully embrace Mailbox. I set up all my mail accounts, aliases and signatures. I also transformed the few classic IMAP folders I had into Mailbox lists. This can be done by moving the folder into the Mailbox folder. Lists are plain IMAP folders in the background, so backwards compatibility should be no problem.

The last time I was this happy with my mail Apps was when Sparrow for iOS was released.