I wasn't aware of the existence of sabre-zarafa until now! I wasn't able to get z-sync to work until yesterday (it deleted my whole addressbook on start, tough!!! good to have backups....) but now it works.
I was browsing the zarafa plugin page where I've found Levelbossmike and it worked nearly out-of-the box, except for the character-coding problem. It could be related to Thunderbird/SoGo as well, because my patch doesn't work with Thunderbird 10.1.
I'm going to investigate this, on the top of the howto I've already added a compatibility matrix.
I also mailed the Levelbossmike developers, their solution seems to be better to me at the moment (open source and free of charge, relies on the SoGo connector = more developers) than z-sync.
It would be interesiting to see, how many Zentyal/Zarafa users need a native Linux client? Responses are welcome!