I don't quite understand how GMS syncs contacts. On my Treo, I have
contacts in either a "Personal" or "Business" category. I then log into
the GMS web interface, say pick contacts to sync, and choose the "Joseph
Marton" addressbook along with unfiled. Any contacts that exist on the
Treo get shot up to GW, but if a contact already exists in the "Joseph
Marton" addressbook it's now duplicated on the phone. That's because I
now have a new contact category on the phone, named the same as the GW
addressbook--Joseph Marton.

What exactly is the proper way to do this? Most of the users that will
have this enabled have existing contacts in their phone & in GW, and
chances are some of the contacts exist in both places. With PDA Connect
as an example the categories on the Treo all got synced into one
addressbook in GW; a new one wasn't created on the phone.