Love zim wiki, use it every day, but: it still doesn't detect file change on disk. So after (1) edit on host A, (2) sync with git (or rsync or btsync...), (3) go to already open edit window on host B, you can end up editing a stale buffer, and then you have to merge manually.
It's multiplatform, written in Pyhon, easily extensible and a truly fantastic piece of software that is well worth investigating.