Rated 4 out of 5 stars
I think it is a good plugin (but I like very much the ThunderSync  interative conflict resolution window that I don't found in SyncKolab at the moment)...
On the contrary, I like very much the use of a modern xml standard for data... that ThunderSync has not (at the moment?)...
When it is planned the release of mailing list sync function you could read here:
Have All a nice day,