Sync contacts and Calendar info from both Mac & PC...?

You can sync calendars, contacts, bookmarks, etc., with multiple computers, as long as you have iTunes installed on all of them. You can sync iTunes media content (music, videos, etc.) with only one computer. On the 'second' computer (the one you don't sync iTunes media from), disable automatic syncing, and turn off syncing of everything except contacts/calendars (and bookmarks, if you like).

How exactly does that work? Every time I've tried to do it, I get duplicate appointments on both computers as well as on the iPhone. I also notice that iTunes unselects calendar/contacts when you go from machine to machine. Lastly, I select the "merge" feature so that the calendars are merged but then see an error about the sync engine not being able to complete at which point it stops syncing. I've been working on this for days and can tell you it is not an easy task.

I was using separate calendars, since that made sense for my purpose - my personal calendar from my Mac, and my work calendar from my work-provided PC laptop. Never had duplicates, but I also never tried to keep all three in sync - just home calendar synced with iCal and work calendar synced with Outlook. Initially I had used O2M to export my Outlook calendar to a .ics file, and imported that in to iCal, and only synced my phone with the Mac. Once my company started allowing iPhone Exchange account access, I no longer needed to sync with Outlook.