Hello,
I reformatted the machine I was using for openCRX so I'm working on getting it setup in a virtual machine.
I had a problem with exports in the past when the field External links (under System?) wasn't filled in. That field should contain the UID of the contact. Once I get my virtual machine running I can give you better instructions.
The add-on as of 0.1.0a1pre1 can only perform an "Import" or "Export" instead of synchronizing the contacts. An import first clears the destination address book then gets the contacts from openCRX and adds them to the address book. That will cause any new contacts not on the server to be deleted.
I plan on eventually adding support for openCRX in my primary add-on, gContactSync (very roughly ~9000 - 10000 users/day versus ~10-15 for the openCRX add-on), in version 0.4. However, I haven't even started working on 0.4 (0.3 isn't even out of the alpha/testing stage) so it might be time for an update to the add-on.
I did start working on editing existing contacts during an import but never completely finished or tested it enough for a release. Now that you have shown interest I'll try to take a look at it.
Josh