Scarab & Brian, good discussion. I was on the same page a few months ago.
If you do a survey of smartphone users, I'm guessing over 98% access email with the built-in smartphone client/app. It's because users want convenience and things like push notification, contact syncing, calendar integration, etc. Hardly anyone (except for Scarab's boss :-) uses webmail on a smartphone, regardless of platform (Yahoo, Gmail, etc.).
So instead of spending 6 months writing a mobile-friendly interface for 2% of users, spend the time writing code for the 98% that makes it easier and less expensive to configure and use your mobile device. For example, write an app or make a URL that sets up IMAP+CalDAV+CardDAV on a smartphone so it's as simple as ActiveSync where all you have to do enter your email address and password (no server names, no ports, sync mail, contacts, calendars, notes, & reminders).
This would make our life as a mail admin so much simpler and give our users a better experience. This might only take a month or so and ST could spend the remaining 5 months adding bonus features: