I sync 17 calendars in one Outlook profile to my BlackBerry Bold 9700 locally over USB, and without the ability to seamlessly do the same with another device, I can't and won't switch.
Everyone I know asks me why I still use a BlackBerry, and it's exactly for this reason: No other device out there handles calendaring as well as the BlackBerry. Most of them consider PIM apps (and calendaring) to be an after-thought, a "bolt-on", but RIM puts it right in their core competencies.
How do you sync multiple calendars on a Blackberry? Sounds like you have BIS. Can this be done through BES?