I have been doing quite a bit of work on this now. - Calendar only so far.
1. When I set the options to delete the calendar on my device, it does just that. However it does not recreate them from the Exchange server.
2. When I set the option to not delete the items on my device, then it duplicates them on the server. I have single items on my device and duplicate items on my Desktop PC.
It gets better....
So I backup my calendar on my desktop and then delete everything. Sync again and appointments still exist on my 4700. So let's delete everything.
Now I have no appointments on my ipaq and no appointments on my desktop. OK so this should be a good place to start. Sync it now and there is nothing at all. Now import the file into outlook on my desktop and ... Yes I have all my appointments back. So sync it again. And still my ipaq contains nothing.
Disable calendar sync with the server, and re-enable to desktop and my appointments get synchronised.
Considering that Activesync 4 will rely on this fow WiFi syncing, I should hope that it works a bit better than this.