You do not need Missing Sync to sync Address Book and iCal. You just need iSync and to enable Palm OS Syncing. Basically, this allows you to sync your iApps instead of using Palm's Calendar/Contacts.
Missing Sync does provide additional features. For example, if you have a removable media card in your Treo, it will mount in iTunes making it easy to put music on your Treo. It's more of an extension of capabilities, rather than a necessity. For bare bones syncing, Palm Desktop will suffice.
-Chris |