Thanks for your respons Linada,
Regarding the philosophy: I see.
On your experience, I understand. But frankly, apps like iCal and Addressbook are too simplistic in themselves when volume and/or complexitiy has to be handled.
About the Sync system I described, I don't mean MobileMe, which is a subscription service for external syncing. In OS X there seems to be a sort of go-between database that is used by apps (and iPhone) that sync with one another on a single Mac. I first found it described in the manual of one of the programs I tested, I think it was Daylite. That go-between also explains why I can sync OF and CP while iCal is not even running.
Regarding the need for an integrated PIM:
Check
this very recent thread, it descibes one of the problems with separated apps quite nicely.
Furthermore, once you have intense email communication and zillions of processes and documents to handle, the way of working you advocate means a lot of clicking and switching between apps. Mistakes, failures and losses are just bound to happen, I have seen it so often. Outlook, CRM progs and document management systems are so popular for very good reasons.