I had to synchronise a T630 with OpenSync [1] and couldn't really finish the job unless I did find out, that the phone doesn't like syncing some stuff. Now I omit syncing "Events" and "Notes":

mysnctool -sync setupname --filter-objtype note --filter-objtype event

It works like that, though I seem to have problems with pictures in vCards being duplicated on every synchronisation. Just deleted them all in my local addressbook, so the phone has enough memory free for the entries.