Well, I'll admit that I've never used the HTC Sync with my Sprint HTC Hero, but I sync Outlook Calendar with the Hero via Google Calendar.
I have Outlook 2007. I downloaded
Google Calendar Sync and it automatically syncs bothways between Outlook 2007 and Google Calendar. And since the Hero automatically syncs the Google Calendar with the Hero, it all just works. So, I just use the Google Calendar on the Hero, and have the My Calendar disabled. No matter where I edit or create a Calendar event (Outlook, Google Calendar, or the Hero), it just syncs all the way around.