I downloaded Mulberry to take it for a spin. At first the interface complexity really is a shock, but I got used to it pretty quickly. I don’t think I’ll be paying money for it, despite how well it does IMAP. Mail.app isn’t unusably bad in that respect. Some thoughts:
- No support for AppleScript or other alternative scripting language
- keyboard shortcuts don’t seem to be arbitrarily (re)assignable
- Tabs/rest of interface can’t be navigated fully by keyboard (my biggest problem w/ Mail.app)
- No mailbox list filterings (a la Mozilla – or even better, the ability to create complex filters as views), also option to hide deleted/but not expunged messages, etc
Related: the CMU HCII actually did a usability study on improving Mulberry’s interface last year.